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Show 74 ZOOLOGY OF TilE VOYAGE OF TIIE BEAGLE. The fossi·l remam· s here descn' b c d wet ·e <.] 't scovet ·ed by Mr · Darwin in. the same bed of partly consolidated gravel at Punta Alta, Northern Pat~goma, as that in wht·c h the lower J· aws o f t 11 e '1.'o xo<1 o n a nd Jlf1,,1 lodon w.e re Im. bedded. The parts of the skeleton about to be described were discovered m then natural relative position, as represented at Pl . XX ., 1· n d'1 ca t'm g, Mr · Dar. win observes ' that the sublittoral formation in which they had been originally depostted had been sub-ject to little disturbance.* 1.'hey include the cranium, nearly entire, with the teeth and part of the os hyoides; the seven cervical, eight of the dorsal, aud five of the sacral vcrtebrre, the two scapulre, left humerus, radius and nina, two carpal bones, and an ungueal phalanx ; both femora, the proximal extremities of the left tibia and fibula, and the left astragalus. The principal parts of the cranium which arc deficient are the anterior extremities of both the upper and lower jaws, the os frontis, rethmoid bone, and the whole upper part of the facial tlivision of the skull ; but sufficient rernains to show that the geueral form of the skull resembled an elongated, slender, sub-compressed cone, commencing behind by a flattened vertical base, slightly expanding to the zygomatic region, and thence gradually contractiug in all its dimensions to the anterior extremity. The Cape Ant-eater (Orycteropus), of all Edentata, most nearly resembles the present fossil in the form of its cranium, and next in this comparison the great Armadillo (Dasypus gigas, Cuv.) may be cited: on the supposition, therefore, that the correspondence with tl!e above existing Edentals observable in the parts of the fossil cranium which do exist, was carried out through those which are defective, the length of the skull of the Scelidothere must have been not less than two feet. If now the reader will turn to Pl. XXI. he will see that this cranium is singularly small and slender in proportion to the rest of the skeleton, especially the bulky pelvis and femnr, of which bones the latter has a length of seventeen inches, and a breadth of not less than nine inches; the astragalus, again, exceeds in bulk that of the largest Hippopotamus or Rhinoceros; yet the condition of the epiphyseal extremities of the long bones proves the present fossils to have belonged to an immature animal. Hence, although the Scelidothere, like most other Edentals, was of low stature, and, like the Megatherium, presented a disproportionate development of the hinder parts, it is probable, that, bulk for bulk, it equalled, wben alive, the largest existing pachyderms, not proboscidian. There is no evidence that it possessed a tesselated osseous coat of mail. I shall commence the description of the present skeleton with the cranium. " This beach is covered at spring tides; m:my parts of the skeleton were encrusted with recent Flustnv and small marine shells were lodged in the crcvic~-s between tho bones. ' FOS lL :MAl\Li}l AUA. 75 ~h~ con.dylcs .o~ the occiput (See Pl. XXI. fig. 2,) arc wide apart, sub-elliptic, very sun.ll~r m ~OSitiOn, form, and relative size to those in Oryctcropus. The foramen occ1pttalc 1s transversely oval, its plane slopes from above downwards and forwards at an angle of. 40° w~th tl~at of the occipital region of tlw skull. This region, as before stated, IS vertical m position (see fig. 1, Pl. XXI.), of a sub-semicircular form, the breadth being nearly one-third more than the height; it is bounded above and laterally by a pretty reo-ular curve ; hut the superior margin is not produ?ed so :ar b::~ckwards as in Orycteropus. The occipital plane is bisected by a mesml vert1calndge; there is a less developed transverse curved inter-muscular crest wl.tich r~us paral.le: with and about half an inch below the marginal ridge: the surface of the occlpttal plane on the interspaces of these ridO'es is irre()'ularly . l . I b o ptttC( wit l the impression of the iusertion of powerful muscles. The coiTcs-ponding surface is smooth in the Orycterope and Armadi11os; in the great extinct Glossothcre it resembles in chamcter that of the Scclidothere; but in the forward slope of the occipital plane the Glossothere differs in a marked degree from the present animal. The upper surface of the cranium is smooth and regularly convex. The extent of the origin of the temporal muscles is defined by a slightly-raised lnoad commencement of a ridge, which, in the older animal, might become more developed. ,..fhcre is no trace of this ridge in the Oryctcrope ; but it exists in the Armadillos, iu which the teeth are of a denser texture, and better organized for mastication, and consequently are associated with better developed masticatory muscles. It will be subsequently shown that the Scclidothere resembles the Armadillos in so far as it possesses a greater proportion of the dense ivory to the external coomeutum in its teeth, than does the Mcgatherium; while it differs widely from tl1e Orycterope, in the structure of its teeth. The teeth, however, are fewer in the Scelidoth re than in any Armadillo, anu relatively smaller than in most of the species of that family. Accol'dingly we find that the zygomatic arches are relatively weaker; and in this particular the Scelidotllere con·e ·ponds with the Orycterope. The zygomatic process of the temporal commences posteriorly about an inch and a half from the occipital plane, its origin or base is extended forwards in a horizontal line fully four inches, where it tenuinates as usual in a thin concave edge, as shown on the right side in Pl. XXII. The free portion of the zygoma, continued forwards from the outer part of this edge, is a slender sub compressed process, half an inch in the longest or vertical diameter, and less than three lines in the transverse; the extremity of this process is broken off'; the opposite extremity of the malar portion of the zygoma is entire, and obtusely rounded. The bony arch may have been completed by the extension of the temporal process to the malar one, but the two parts undoubtedly were not connected together by so extensive a surface as in |