1886.] MR. R. L-VDEKKER ON SCELIDOTHEKIUM. 491 



Plate XLV. 



Pig. 1. Outer aspect of the right pelvic limb of Geococcyx californianus showing 

 the third layer of deep muscles, with a dissecting-chain pulhng 

 the ambiens into view. Life size, by the author from his own dis- 

 sections. 

 2. Outer aspect of pelvis and right pelvic limb of Geococcyx californianus. 

 Designed to show the deep muscles of the region, and the bones 

 have been slightly rotated from their normal positions in order to 

 bring them into view. «. Vinculum between deep flexor and flexor 

 longus hallucis. Drawn by the author from his own dissections. 



3. Description of three Species of Scelidotherium. 

 By R. Lydekker, B.A., F.G.S., F.Z.S., &c. 



[Eeceived September 20, 1886.] 



(Plates XLVT.-XLIX.) 



In the ' Zoology of the Voyage of the Beagle/ published in 

 1840, Prof. Sir Richard Owen founded the genus Scelidotherium on 

 the evidence of a considerable portion of the skeleton of a large 

 megatherioid Edentate found fay Darwin in the Pleistocene of Bahia 

 Blanca, in Patagonia, and applied the specific name of lepto- 

 cephalum. In the following year and in 1842, Lund published in 

 the volumes of the Copenhagen Academy descriptions and figures 

 of more or less imperfect remains of various allied animals from the 

 Brazilian caves, all of which were eventually referred either to 

 Owen's genus or to the new genus Platyomjx, no less than seven 

 new specific names being applied to these specimens. In 1850 

 the late Prof. P. Gervais published, in the results of Castelnau's 

 Voyage (' Mammiferes fossiles de I'Amerique meridionale '), a de- 

 scription and figure of a skull from Buenos Ayres which he referred 

 to the type species of Scelidotherium, and also of a second one from 

 Tarija in Bolivia, which he did not name specifically but thought 

 might be a new species. In 1857 Sir Richard Owen published a 

 second memoir in the ' Philosophical Transactions,' in which he 

 described and figured two skulls brought over in 1854 by Bravard 

 from the Pleistocene of the Argentine Republic, both of which he 

 referred to the type species. An important notice of the group 

 was contributed by Dr. H. Burmeister, of Buenos Ayres, in his 

 ' Description Physique de la Republique Argentine' ' (18/9), where 

 he described a skeleton which he likewise referred to the type 

 species, and also gave reasons for adopting Lund's genus Plutyonyx 

 for some of the allied forms. In 1880 Messrs. H. Gervais and 

 Ameghino, in a memoir published under the title of ' Mammiferes 

 fossiles de I'Amerique meridionale,' gave a synopsis of all the 

 previously named species of Scelidotherium and Platyonyx, and 

 applied the new specific name of S. tarijense to the above-mentioned 

 skull from Bolivia, figured by P. Grervais ; and also founded a second 



1 Vol. i. part iii. pp. 322-345, pi. xiv. There is no copy of the Atlas in any 

 of the London libraries. 



