TESTUDO ELEPHANTINA. 25 The female (spec. e) does not differ much from the male as regards the form of the carapace; but, being evidently a much younger specimen, the striz are deeper, more numerous, and more distinct. The nuchal plate is, exceptionally, absent. The sternum is nearly flat, with a distinct notch in front and behind. Tail short, with a terminal claw. Colour as black as in the male.
The very young specimen, which is only 14 inches long, has the scutes very neatly sculptured, deep concentric striae occupying nearly the whole of the scutes, with the exception of the small areolar spaces. The carapace itself is high, of a regularly oval shape. Sternum scarcely notched in front and behind. Colour less intensely black than in the preceding specimens.
The measurements of these specimens are as follows :— Length of carapace. Width of carapace. Depth of Sternum. Caudal plate. Instr.line.Overcurve.Instr.line.Overcurve.carapace.Length.Width.Length.Width. in. in. in. in. in. in. in. in, in.
PCEEOG) cies a6 49 643 364 65 26 38 25 4, 84 JN(Gly fey BAeROn 39 52 26 54 24, 32 23 34 9 9 2\(0 SO 274 36 22 37 134 234 174 34 64 Miooe eeaiestsc 14, 183 8 18 84 124 4 1} 34 VarietyB.
Of this variety I have only one incomplete example before me (if, indeed, the very young specimen just described should not be more properly referred to it)—a large carapace 40 inches long, the sternum of which is lost. It differs from the preceding variety in being horn-coloured, and in having the carapace conspicuously narrower and somewhat less elevated. ‘The protuberances of the costal plates are less pronounced ; and the upper profile of the last vertebral and caudal sweeps downwards in an uninterrupted gentle curve. The broad areolar portions and the striations of the scutes are exactly as in the preceding variety; nuchal plate of moderate size, as long as broad. Length of carapace. Width of carapace. Depth of Caudal plate. In str. line. Over curve. Instr. line. Over curve. carapace. Length. Width. in. in. in. in. in. in. in.
ENG GGusiavsisiet 40 504 234 49 163 4 sf) Variety y.
The adult male has the carapace broad and depressed, nearly equally wide in front and behind; its upper surface is remarkably flat, and the anterior slope considerably steeper than the posterior ; in fact the median profile of the first vertebral scute between its hind margin and the nuchal plate is remarkably concave. The anterior free margin of the carapace is somewhat turned outwards, but not reverted, and without any notches, whilst the posterior shows a reversion with shallow notches between the marginal scutes. E
26 THE RACES OF ALDABRA. Also the caudal plate is slightly bent outwards, with a rather concave surface. The high humps of the vertebral and costal scutes, which are so conspicuous in variety a, are here entirely absent; but in all the scutes the smooth areolar portion can be clearly distinguished from the very broad striated portion, the strize being rather wide. The sternum is deeply concave, broad, with the anterior portion not conspicuously contracted, and with a shallow notch in front and behind, the substance of the caudal plates and of the lateral portion of the abdominals being thickened and callous. In the scutellation of the head and limbs this variety does not differ from variety «; also the tail is nearly of the same length and provided with a flat terminal claw. ‘ The carapaces of the younger specimens agree in the essential particulars with the larger; but they are decidedly higher, the surface of the costal plates being more vertical and the slope of the anterior vertebral scute less steep. The colour of the three specimens is black, with a horny tinge about the areolar portions. The measurements of these specimens are as follows :— Length of carapace. Width of carapace. Depth of Sternum. Caudal plate. Instr.line.Overcurve.Instr.line.Overcurve.carapace.Length.Width.Length.Width. in, in. in. in. in. in. in. in. in. ORO @e canis 43 50$ 30 50 203 31g 26 34 9 (NG Ga cuameves 40 52 30 52 183 32 24. [2] 10 H.-gr.g ... 31 41 ks) 40 We [?] 18 3 i Heer. Sd <.. 295 38 18 40 15 23 17 ae 7 Osteology.—In the preceding remarks, as well as in the following notes on the osteological characters of the various species, it is not my intention to give such a complete description as would include every detail common to all the species of Testudo, but I shall limit myself to those points only by which the various species of gigantic Tortoises differ from one another in a marked manner. The skull, figured on Plates VIII. & IX. fig. A, measures in length from the occipital condyle to the extremity of the snout 53 inches, and from the extremity of the occipital crest to that of the snout 64+ inches; its greatest width is 4$ inches. Large as this skull is, it is surpassed in size by that of specimen c, the corresponding measurements of which are 6, 64, and 43 inches. In the details of their structure and configuration these skulls are perfectly identical. They are distinguished from those of the other species by the very shallow excision of the hind margin of the paroccipital, and by their great relative breadth. 1*. The frontal region is raised and convex, broad, its greatest width (in front of the postfrontal) being one half of the distance of * In this and the following description of the skulls the same points are notited under the same numbers— a plan by which the comparison of the several parts (sometimes described many pages apart) is much facilitated. The significance of certain modifications of structure noticed here will become more apparent when we shall treat of the skulls of the Mascarene and Galapagos Tortoises.
TESTUDO ELEPHANTINA. OF, the tympanic condyles (outside measure). 2. The upper surface of the parietals is a flat triangle, the outer edges of which converge towards, and finally are merged into the tetrahedral occipital crest, which is of moderate length. 3. The tympanic case with the mastoid is not produced backwards; sothat the posterior margin of the paroccipital is but little excised. 4. The groove on the lower surface of the occipital, in front of the condyle, is very shallow; no styloid process on each side of the condyle. 5. The prominent tuberosity on the front margin of the temporal fossa, which in some of the Galapagos Tortoises is so much developed, is but feebly indicated. 6*. The tympanic cavity is of moderate extent, the outer tympanic rim having an irregular outline, like that of an inverted human concha, the convexity being anterior. In its posterior margin there is a very deep triangular excision for the passage of the Eustachian tube. 7. This excision is so deep that it nearly extends to that part of the bottom of the cavity which is pierced by the foramen for the columella; this ossicle, therefore, does not rest on a trenchant ridge as in the Galapagos Tortoises. 8. The front margin of the intermaxillaries projects so much beyond that of the frontals, that the nasal opening slopes obliquely downwards and is much higher than broad. 9. The inner nostrils are situated far back, and, on the palatal view of the skull, may be seen free and uncovered by the alveolar lamelle of the maxillaries. 10. The intermaxillaries are long, about two thirds the length of the maxillaries ; and their foremost portion is neither very concave nor much bent downwards to form the beak. The suture between the intermaxillary and vomer is at a considerable distance behind the inner angle of the alveolar edges of the maxillaries. 11. The whole of the palatal region is deeply concave, with a very low median crest along its bottom. The triangular space of which the foramina palatina and the anterior extremity of the vomer form the points is isosceles. 12. Anterior surface of the tympanic pedicle deeply excavated. 13. Lower jaw with a double alveolar ridge, the symphysial portion being simply vertical, without a backward dilatation of the lower margin of the bone. The description of the other parts of the skeleton is taken principally from the adult male specimen ¢ and from /, a male not fully grown, with a carapace 31 inches long.
The cervical portion of the vertebral column is comparatively much shorter than that of the Galapagos or Rodriguez Tortoises; the several vertebra are shorter and thicker ; the crests are lower, without additional lateral crests; the majority of the posterior articulary processes have a strongly divergent outward direction, the notches between - them being very wide and deep; and the anterior are nearly perpendicular to the * It is very singular that although the osseous parts of the auditory organ are so well developed, nevertheless, accordingtotheunanimoustestimonyofobservers,theseTortoisesareabsolutelydeaf.Ifindthisconfirmedsofarinmyyounglivingexample,thatitnevertakesnoticeofthenoisyapproachofapersonwhomit cannotsee,norisitdisturbedbythefallofastonebehinditsback.Perhapsthefacultyofhearing,although never acute, is not entirely lost until the individuals have attained to a great age.
E 2
28 THE RACES OF ALDABRA.
longitudinal axis of the vertebree. All these characters are indicative of a comparatively shorter neck with lessened power of turning, as we actually observe it in the living animals, although it must be remembered that the length and mobility of the neck of these Aldabra Tortoises is still much greater than in any of the smaller forms of the genus Testudo. Most remarkable is the peculiarity in the articulation of the third and fourth vertebree, which in all the Flat-headed Tortoises (from the Galapagos as well as Mauritius and Rodriguez) is reversed.
In the atlas of the younger individual the lateral portion of the neural arch (column) is very broad, considerably broader than the zygapophysis, which is rather shorter than that part of the bone which forms the roof of the arch. ‘These parts are separated from one another by less-deep constrictions in the adult specimens, the lateral portion being nearly as broad as the zygapophysis (Plate X. fig. A). ‘The centrum (odontoid process) is as broad as long in the adult, and broader than long in the young, with oblique articular surfaces, two in front and one behind.
In the second vertebra (Plate X. fig. B) the neural arch is somewhat compressed, provided with a low crest. The third has a condyle in front and behind, the posterior being much elongate and reaching beyond the extremity of the zygapophyses (Plate X. fig. C). The fourth has a glenoid cavity in front and a condyle behind; there is a marked hollow in the neural arch behind the anterior zygapophysis in the adult specimen, which is absent in the young, clearly showing that this peculiarity is developed with age. The fifth has a single low median neural crest (Plate XI. fig. A), and a deep hollow behind each anterior zygapophysis. ‘The s¢xth has a glenoid cavity in front, and a broad, depressed, bipartite condyle behind; its dorsal surface is much compressed, with a short, high, triangular crest, whilst on the visceral surface a lower crest runs for about two thirds of its length and bifurcates behind (Plate XII. fig. A). The seventh (biconcave) vertebra (Plate XIII. fig. A) is distinguished by the high crest on its dorsal and visceral surfaces; in the middle of the vertebra the neural crest is split into two branches, diverging in the direction of the posterior zygapophyses and leaving a deep triangular recess (a) between them. The point of divergence forms a kind of summit (0) to this vertebra, which, however, is overtopped by the extremities of the anterior zygapophyses. The place on the neural arch inwards of and behind each anterior zygapophysis is not hollowed out, as in the Galapagos and Rodriguez species, and is even much less concave than the corresponding portion of the preceding vertebre. ‘The anterior and posterior glenoid cavities are completely divided into a right and a left half in the adult, and less completely in the young specimen. ‘The eighth vertebra (Plate XIV. fig. A) has a bipartite anterior and single posterior condyle, the posterior zygapophyses being curved downwards. to the level of the condyle.
The measurements of the second to seventh cervical vertebree are as follows :—
TESTUDO ELEPHANTINA. 29 2nd. 38rd. 4th. Sth. 6th. = 7th. millim.
millim.
millim.
millim.
millim.
millim.
Adult 70 106 105 112 120 += 105 Young 37 61 57 64 69 60 Adult 45 48 50 53 68 78 Young 29 28 29 33 46 46 Adult 25 25 27 29 53 56 Young 17 16 17 18 25 30 Adult 28 28 7 Young 15 16 i me bis bad AGOG 1.5 oie 35 4.2 50 58 Tenethyolscemirunys 9.3225 fetes s sina 500s Depthofcentruminthemiddle............... Horizontalwidthofmiddleofcentrum...... Wradth'of anterior’ condyle 2.2220.
.2...40ksae Width of anterior glenoid cavity .............. Noate. os _ oA o7 39 36 Adult... 31 35 44. 56 idth of 1ORICOMOVIC) coer aecveaqanonese Width of posterior condyle Ronee os 20 99 98 35 i. Adult 27 se we ae or 68 - ; ; :
Width of posterior glenoid cavity ............ oun 16 i 7 - 7 39 Distance of outer margins of anterior zyga- ¢ Adult 44. 60 55 59 65 56 OPH SCS Bm WR se oa cria te mendes doce eae Young 22 34. 36 37 40 35 Distance of outer margins of posterior zyga- ¢ Adult 52 50 48 52 48 65 LO URVSCSME te Me maa inners haa aera ces Young 29 32 35 36 32 45 A comparison of this table of measurements with those given of the Galapagos Tortoises shows that in the much shorter vertebre of the Aldabra species all the other dimensions of width, depth, or expansion of articular surfaces and processes equal or even exceed those of the Flat-headed group. Dorsal vertebre.—The two heads of the first rib are rather broad, much divergent, leaving a triangular space between them and the first dorsal vertebra. The iliac bones abut against the pleurapophyses of the 9th, 10th, 11th, and 12th vertebree (counting from the first dorsal vertebra). Their distal extremities participate more or less in the formation of the protuberance for the articulation of the ium. Iam enabled to give the measurements of the dorsal vertebrae of two individuals, viz. of specimens J and m of the list given above. Length of centrum of dorsal vertebrae :-— Individual. Length of Ist. 2nd. 3rd. 4th. 5th. 6th. 7th. 8th. 9th. 10th. 11th. 12th. No. carapace. Mm. mm. mm. mm. mm. mm. mm. mm. mm. mm mm mm. et ee oa 31 in. 45 70 82 86 80 65 48 389 24 19 16 16 ae 293in. 43 70 7 76 7 57 40 29 #19 17 [lost] The number of caudal vertebre is twenty-five, of which the last seven are coalesced into a single bone. The centrum of the first (Plate XV. fig. A) is without hzmal crest, and so exceedingly depressed, thin, and flat, that the anterior glenoid surface is reduced to a pair of small lateral tubercles, and the posterior condyle is transversely hnear; on the other hand, the neural arch forms an unusually thick mass of an oblongo-tetrahedral shape, bridging over the spinal canal, which in this part is very wide, broader than high.
30 THE RACES OF ALDABRA.
The prezygapophyses face towards the dorsal, the postzygapophyses towards the visceral side; both are oblique, the former separated from each other by a very narrow groove, the latter by a crest. The continuity of this vertebra to the lumbar is indicated by the development of a long diapophysis flattened and dilated at the base. The second caudal resembles the first, approaching in form the third, the principal difference from the first being the reduction in length of the diapophyses. Whilst still retaining the massive neural arch, the third, fourth, and fifth caudals (Plate XV. fig. B, the fourth) have also their centrum thicker than the preceding vertebra, the posterior condyle being subglobular, with an obtuse hemal ridge arising from it. Their prezygapophyses are subvertical, separated by a groove, which is now wide enough for the passage of the blood-vessels, which branch off from those of the spinal canal, and carry the blood through a foramen situated in the median line between every pair of vertebre to or from the back of the tail. The postzygapophyses are likewise separated by a groove forming one half of the canal for blood-vessels. Diapophyses obliquely directed forwards. In the stvth (Plate XV. fig. C) the centrum is shortened, thicker, more distinctly compressed ; diapophyses long, directed forward; preezygapophyses obliquely facing dorsad, widely separated by a semicircular notch, and much more expanded than the postzygapophyses. ‘The spinal canal has become narrower, and is deeper than wide. The following vertebra, from the seventh (Plate XIII. figs. D, D’, D”, ninth vert.) to the eightcenth (Plate XIV. figs. C, C’, C’, C’”), are built upon the same plan, the gradual modifications being the following:—the centrum becomes shorter and, like the whole vertebra, more depressed; a hemal ridge soon becomes quite obsolete; the anterior glenoid cavity lower, shallower, and relatively broader; the posterior condyle less prominent, loses its globular form, and becomes lower and transverse; the diapophyses stand at a right angle to the axis of the centrum, lose in length, retaining their relative breadth at the base; the neural arch loses in substance and is depressed, nearly flat above; the neural canal, again, becomes wider than deep. The last seven vertebre are quite rudimentary and coalesced into a single bone.
Possibly the extraordinary development of the neural arch of the anterior and of the neural arch and centra of the succeeding vertebre is peculiar to males of such an advanced age as that was from which the foregoing description is taken. In individuals of that sex the tail plays a very important part as an external prehensile, or rather steadying organ, which also differs externally from that of the female in its greater length and by being provided with a large terminal claw. Nearly always the animal carries it bent sidewards under the carapace, generally towards the left side; and therefore I anticipated to find a want of symmetry in some portion of the root of the tail; however, nothing of the kind can be observed. ‘The articulations between the first four vertebre are so complex that their mobility must be very limited indeed, whilst in the six following the anterior glenoid cavity is disproportionately large for the small size of the condyle; and this seems to be the part where the lateral flexion of the tail is effected.
TESTUDO ELEPHANTINA. 31 The length of the entire caudal portion of the vertebral column is 27 inches (that of the carapace being 49 inches). Liimb-bones.—The scapulary is stout and massive. The angle at which the scapula proper and the acromium meet is about 100°. The body of the scapula is compressed, trihedral in form, a transverse section through its middle resembling much that of T. elephantopus, delineated in the description of that species: its anterior side is convex, asin that species; but neither of the other two surfaces is so decidedly concave. Shaft of the acromium compressed in its proximal half, subtrihedral in its distal portion. The coracoid is never ankylosed to the scapula, not even in our largest specimens; its neck is much constricted, compressed transversely to the dilated portion of the bone. The measurements of three examples of this bone are the following — Spec.c.Spec.l.Spec.n. milim.millim.millim. Length of scapula (measured from the suture with the coracoid)... 265 172 200 Cireumferencemetsmiddle3.0.5.2hekwesaaeescodedescocucassnssseronses1457392 Wongitudinal diameter of plenoid cavity .....2...........-.seseseseseeees 90 53 Mens thgomcOrac0l ds Ae aa e8s cr, 2002 sot tes @ opts Eis co when Sea tan dnccebiw as 150 100 Greatestawld theo COPACOld: —4055...se..54¢. 0k ssacdmndttsbesntehssceveaeiaenes 133 80 WeroUneoImaCOMMUNetertectatssnesceoxeeAeeccasacssesPateeecnah'sseas1107890 The shaft of the hwmerus (Plate XVI., taken from specimen ¢) is broad and stout, slightly bent, trihedral in the adult, and compressed in the direction from the front backwards. ‘There exists a distinct impression on the outer side of the bone, immediately below the head and ulnar tuberosity, and another deeper one on the hinder side above the trochlea. Both the radial and ulnar edges are much curved. The ulnar tuberosity projects high above the head, which, again, is raised (but not entirely) above the level of the summit of the radial tuberosity. The canal for the blood-vessels on the radial edge of the bone, close to the elbow-joint, is perfectly closed, perforating the substance of the bone from the front to the hinder side. Spec.c.Spec.l.Spec.n. millim.millim.millim. Lengthofthehumerus(measuredinastraightlinefromthesummitof cheshead).torthemiddleofthetrochlea)......5...0cc.-sesescotfeesaverteesases308180195 Circumference of the narrowest part of the shaft .................0......: 160 81 100 Moneest, diametersot the Head) jax.
.icc.c.sexsen sien csnecuscecereeierveevteterse sees 80 39 39 Shontes mliaimetery Ol tUCsMeA ds wayevinscveyst ese.
eire ce-ch sartusd ees cise dense deans 60 34 35 lxtreme: breadth: between the condyles. ............0<:.ic.cse. Geessesecdaeeseass 125 66 76 The bones of the forearm need scarcely any description beyond giving the measurements. The shaft of the radius has the ulnar edge rounded off and obtuse. In the larger examples the olecranon is scarcely more prominent than in the younger one, and much less so than in T. daudinit.
32 THE RACES OF ALDABRA.
Spec.c.Spec./.Spec.k.
millim.millim.millim.
Thensth*ofmulna “77 ase rete eee a eee 195 110 142 east widthsof ulna! 3s ee) ere eee 31 18 22 ength*oigradiusy a sete ero eee 175 97 130 Least circumference of radius ............... 85 40 63 The general arrangement of the carpal bones does not differ from that of the Galapagos Tortoises, in the description of which it will be more fully noticed. The scaphoid and intermedium are entirely coalesced, even in the younger example; but all the other ossiclesareseparate.
Important and striking as the differences are that obtain in the pelvis of the Flatand Round-headed Tortoises, the various species of the latter form (as far as known at present) differ but slightly among themselves in this portion of the skeleton. The symphysial bridge is strongly compressed, and raised into a trenchant vertical ridge below and sometimes above. Singularly, in our large specimen ¢ all the sutures are as persistent as in the smaller one, so that the bones readily separate ; in the latter specimen all the epiphyses are much less ossified, and the protuberances and processes in a much less developed condition, than is observed in other parts of the skeleton of this individual: the pelvis appears to be the last part of the skeleton assuming the proportions and shape of the adult stage.
The horizontal diameter of the pelvis (Plate XVII.) exceeds in length the longitudinal. The iliac bones are broad and stout; the anterior portion of the pubic bones is nearly horizontal, rather obtuse in front, without median crest below ; it emits laterally a long strong process, which is obliquely directed outwards. The posterior part of the ossa ischii is of great width, scarcely concave above, terminating in a short hamate posterior process on each side, and provided with an exceedingly high symphysial crest below, which, expanding hindwards, forms a large triangular tuberosity. Lateral margin of the ossa ischii excised in the shape of a C. Obturator foramina very wide. / Spec. c¢ . millim Longestinnerverticaldiameterofpelvis(fromsummitofiliumtosymphysis)......200 Longestinnerhorizontaldiameter................ce0se00:febadbesAbARtobeeoaeeeeee230 Shortestinnerhorizontaldiameter(betweenilio-pubicprominences)..................140 ihongest diameter of foramen obturatorium ~~y.42 9-9 .-eee ee ee 73 Widthof symphysial bridge... 20 cucc0. Fo Ua dae se eee 35 Depth of symphysial bridge™. 22. asss..20. 0 nce ee eee eee ee eee 60 Least. breadth of posterior portion of ossa ischit (221 ee ee 114 Liengthiof os tit iipn.8 ced cies ceed sen. Sree oo ce ne ee eee 183 Least breadth of os ili ..... AO et a eee me EAR aE oo 2640.0 boc 090080 c 50 The shaft of the femur (Plate XIX.) is rather stout, nearly straight, irregularly subtetrahedral, narrower in front than behind. The head hasan abbreviated ovate form, and