69 
It has been suggested that the two skulls in the Museum which 
have been extracted from skins of Bradypus crinitus, may both belong 
to male or female animals, and that the skull here described may 
belong to the other sex. As this is a matter of doubt which can only 
be settled by the examination of more specimens the sexes of which 
are known, I have considered it desirable that the skull should be 
figured and described. I may remark that the form of the hinder side 
and angle of the lower jaw of all the three specimens of these skulls 
are very similar. 
Skull. ; B. torquatus. B. affinis. 
in. lin. in. lin. 
PMU <atae as Meee oe at eee ess 2 95 
Lenpth sof palabes eis. oko a ens | aoe 
from palate to occipitalhole. 1 4 
Breadth at occipital ridge........ 1 44 1 24 
at front of ear-hole ...... 1S 1 23 
at front of zygoma ...... 1 10 1 8 
Lower jaw. 
Renpth'’. 397073, BAIS O96. of of 24 2 24 
Width at condyles.............. 1 8 1 43 
of back part of them ...... 0 11 0 10 
III. Arcroriruecus. Bradypus, sp. Riippell; Pr. Mazx.; Cu- 
vier, Oss. Foss.; Blainv. Acheus, F. Cuvier, Dent. Mamm. t. 78. 
Tardigradus, sp. Brisson. 
Hands and feet three-clawed. Skull rounded above on the fore- 
head. Grinders: front upper very small, cylindrical; front lower 
smaller than the others, subcylindrical. Pterygoid separate, com- 
pressed, erect, thin, simple. Intermaxillaries none. 
Lower jaw not produced on the upper edge between the teeth, but 
slightly keeled in front of the chin. 
Face with a black streak from the back angle of the eye. 
Cuvier, Oss. Foss. v. t. 4, figured the skeleton, and t. 5, the skull 
and bones of the feet of this genus; the skull is copied R. A. Illust. 
t. 70. f. 1a. Wiedemann, Arch. Zool. und Zoot. i. t. 1 and 1*, and 
Spix, Cephal. t. 7. f. 12, figure the skull, and Blainville figured two 
skulls belonging to this genus in his ‘ Osteographia.’ 
In the young skull there is sometimes a slight projection on the 
front edge of the zygomatic arch, assisting to form the back edge of 
the orbit, but this process seems soon to disappear as the animal 
increases in size, and I have not found it in any of the older skulls. 
Cuvier, Desmarest, and most French authors, have considered all 
the individuals of this genus as belonging to one species, and have 
given an indefinite description, so as to include them. Cuvier (Rég. 
Anim. ed, 1. 217) thus describes that species : “‘ Sa couleur est grise, 
souvent tachetée sur le dos de brun et de blanc: plusieurs individus 
poeent entre les épaules une tache d’un fauve vif que traverse une ligne 
ongitudinale.” He refers for the species to both Buffon’s figures, 
xii. t. 5 & 6. In the second edition he remarks, “On connait un 
Ai dit la dos brilé, parce qu’il a entre les épaules une tache noire en- 
