1886. | MR. R. LYDEKKER ON SCELIDOTHERIUM. 491 
Prats XLY. 
Fig. 1. Outer aspect of the right pelvic limb of Geococeyx californianus showing 
the third layer of deep muscles, with a dissecting-chain pulling 
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. «a. 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. Lyprexxer, B.A., F.G.S., F.Z.8., &e. 
[Received September 20, 1886.] 
(Plates XLVI.-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 by Darwin in the Pleistocene of Bahia 
Blanca, in Patagonia, and applied the specific name of Jepto- 
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 Platyonyx, 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 (‘ Mammiféres fossiles de Amérique méridionale’), 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 anew 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 République Argentine’ ' (1879), where 
he described a skeleton which he likewise referred to the type 
species, and also gave reasons for adopting Lund’s genus Platyonyx 
for some of the allied forms. In 1880 Messrs. H. Gervais and 
Ameghino, in a memoir published under the title of ‘ Mammiféres 
fossiles de ’Amérique méridionale,’ 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. Gervais; and also founded a second 
* Vol. i. part iii, pp. 322-345, pl. xiv. There is no copy of the Atlas in any 
of the London libraries, 
