749 



MEQATHERIIDJE. 



MEGATHERIIDJE. 



750 



The bones of the cranium connected with the organ of hearing anc 

 an accidental fracture of the right 03 petrosum, demonstatiug its usua 

 dense and brittle texture, and at the same time exposing the cochlea 

 with part of its delicate and beautiful lamina spiralis, give Professor 

 Owen occasion to observe that the conservation of parts of the organs 

 of. vision in certain fossils has given rise to arguments which prove 

 that the laws of light were the same at remote epochs of the earth's 

 history as now ; whilst the structure just alluded to demonstrate, in 

 like manner, that the laws of acoustics have not changed, and that the 

 extinct giants of a former race of quadrupeds were endowed with the 

 same exquisite mechanism for appreciating the vibrations of sound as 

 their existing congeners enjoy at the present day. 



" The brain," says Professor Owen, " being regulated in its develop 

 ment by laws analogous to those which govern the early perfection o 

 the organ of hearing, appears to have been relatively larger in the 

 Scelidothere than in the Glossothere : it was certainly relatively 

 longer : the fractured cranium gives us six inches of the autero 

 posterior diameter of the brain, but the analogy of the Orycterope 

 would lead to the inference that it extended farther into the par 

 which is broken away. The greatest transverse diameter of the crania 

 cavity is four inches eight lines ; their dimensions however are suffi 

 cient to show that the brain was of very small relative size in the 

 Scelidothere ; and both in this respect and in the relative position o: 

 its principal masses the brain of the extinct Edental closely accords 

 with the general character of this organ in the existing species of the 

 same order. We perceive by the obtuse ridge continued obliquely 

 upwards from above the upper edge of the petrous bone, that the 

 cerebellum has been situated wholly behind the cerebrum ; we learn 

 also, from the same structure of the enduring parts, that these perish- 

 able masses were not divided, as in the Manis, by a bony septum, but 

 by a membranous tentorium, as in the Glossothere and Armadilloes 

 in the Orycterope, as has been before remarked, there is a strong, 

 sharp, bony ridge extending into each side of the tentorium. The 

 vertical diameter of the cerebellum and medulla oblongata equals 

 that of the cerebrum, and is two inches three lines : the transverse 

 diameter of the cerebellum was about three inches nine lines; its 

 antero-posterior extent about one inch and a half. The sculpturing oi 

 the internal surface of the cranial cavity bespeaks the high vascularity 

 of the soft parts which it contained, and there are evident indications 

 that the upper and lateral surfaces of the brain had been disposed in 

 a few simple parallel longitudinal convolutions. The two anterior 

 condyloid foramina have the same relative position as the single cor- 

 responding foramen in the Glossothere, Orycterope, and Armadillos ; 

 and the inner surface of the skull slopes outwards from these foramina 

 to the inner margin of the occipital coudyle." 



Dentition of Scelidotherium. 



a. Teeth of upper jaw In itu, seen from above ; b, teeth of lower jaw in situ, 

 nine view ; e, d, teeth, showing the depth of their implantation in the jaw and 

 their ntruclure ; r, crown of tooth, wen from above. Reduced. (Owen.) 



The nine of the orbit U relatively smaller than in the Orycterope, 

 and still lens than in the Ant-Eaters. "Here however," observes 

 Professor Owen, " we have merely an exemplification of the general 



law which regulates the relative size of the eye to the body in the 

 Mammalia. The malar bone does not extend so far forwards in front 

 of the orbit as in either the Orycterope or Armadillo ; in the inclina- 

 tion however with which the sides of the face converge forwards from 

 the orbits, the Scelidothere holds an intermediate place between the 

 Armadilloes and Oryeterope." 



The Dental Formula of Scelidot/ieriuni appears to have been : 



Incisors, ; Canines, ; Molars, = 18. 



4 4 



Though the teeth of Slylodon and Scelidotherium have a close 

 analogy to those of existing small Insectivorous Edentals, there is 

 nothing iu their structure to militate against the presumption that 

 these extinct genera were fed on succulent plants, such as cabbage- 

 palms, or on farinaceous vegetables, such as large ferns. Their teeth 

 are well adapted to chew vegetable tissues of moderate firmness. 

 (' Zoology of H.M.S. Beagle.') 



M. Lund discovered the remains of a large number of fossil Edentata 

 in Brazil. The portion of the country examined by this zealous zoolo- 

 gist is comprised between the rivers Rio das Velhas, one of the con- 

 fluents of the Rio de San Francisco, and the Rio Paraopeba. This 

 tract forms an elevated plateau of 2000 feet above the level of the sea, 

 and is traversed in the midst by a mountain chain only from 300 to 

 700 feet high. The chain is formed by a secondary limestone (calcaire 

 secoudaire) stratified horizontally, and having all the characters of the 

 zechsteiu and the hohlen-kalkstein of the Germans (calcaire a cavernes). 

 It is entirely riddled with caverns, and traversed in all directions by 

 fissures, the interior of which is more or less filled with a red earth 

 identical with the red earth which forms the superficial bed of the 

 country. In this basin of the Rio das Velhas M. Lund has discovered 

 in company with the remains of Ferce, Gtires, Pachydermata, Rumi- 

 nantia, Marsnpialia, Cheiroptera, and Semice, the following mammife- 

 rous fossils, which seem to claim attention here : 



" Family of Edentata. 



"A Myrmecopliaga (GloiiOtherium ? Owen) of the size of an ox 

 (tfyrmecophaga yiyantea). 



" Family of Efodientia. 



" 1. Two species of Dasypws ; one allied to D. octocinclus, and the 

 other twice as large aa the living species. 



"2. Xenunu. 



" 3. Eta-yodon, a lost genus of Tatou, or Armadillo. 



" 4. Heterodon, distinguished from all the living Armadilloes by the 

 proportion of its teeth. 



" 5. C/tlamydotherium, a new genus of Armadillo, representing on a 

 great scale the genus Euphractus of Wagler (the Eucoubert of Bufibn) ; 

 two species, one of the size of a Tapir, the other larger than a 

 Rhinoceros. 



"6. Hoplophorus (Glyptodont Owen), a very extraordinary genus, 

 whether we consider the massive proportions of the species, their 

 gigantic structure, or the singular combination of different types of 

 organisation manifested in them. Their characters nevertheless 

 approach more and more to the family of Sloths. 



" These singular animals were armed with a cuirass which covered 

 all the upper parts of their body, and was composed of small hexagonal 

 scutcheons, except on the middle of the body, where the scutcheons 

 put on a square form and were arranged in immoveable transverse 

 bands. The bones of the trunk as well as the large bones of the 

 extremities are very similar to the Armadilloes (Tatous) and especially 

 to those of the Cachicames [AKMADILLO] ; but the bones of the feet 

 are so abridged and the articular surfaces present such a considerable 

 flattening, that nothing similar is to be seen in any animal skeleton, 

 and one cannot conceive how such feet could serve for digging in 

 the earth (creuser la terre) : the form of the teeth, too, indicates that 

 these singular animals could only have been nourished with vegetable 

 substances, and we must suppose that they fed after the manner of 

 the great Pachydermata. However this may be, the Hoplophori, of 

 which M. Lund distinguishes two species, present this particularity, 

 that their zygomatic arch is furnished with a descending branch, a 

 character regarded till now as exclusively proper to the Sloths. 

 These two species were each of the size of an ox. Fragments of these 

 skeletons have already been described by Messrs. Weiss and D' Alton of 

 Berlin. 



' M. Lund has found fragments belonging to a genus approaching 

 Hoplophorus, and to which ha assigns the name of Pachytherium. Its 

 proportions were still more massive and its stature taller. 



" Family of Sradypoda. 



'M. Lund is thus conducted to the family of the Sloths, which, 'at 

 the Antediluvian epoch,' plnyed in these countries a very important 

 >art, whether the number and variety of their forms, or the great 

 ize which the species attained, are considered. 



" The first genus which he notices is Megalonyx. It is connected 

 with the Armadilloes (Tatous) by the osseous plates which protected a 

 mrt of its body ; but these plates, although of excessive size, fur from 

 brming a continuous cuirass as in the Tatous, were separated from 

 each other by great interval?. The Meyalonyx exhibits the greatest 

 .ffinity to Meyatherium, principally in the structui'r and composition 



