6!) 



It has been suggested that the two skulls in the Museum which 

 have been extracted from skins oi 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. 



Length 2 9^ 



Length of palate 1 2 



from palate to occipital hole . 1 4 



Breadth at occipital ridge 1 4^ 1 2^ 



at front of ear-hole I 5 1 2^ 



at front of zygoma 110 18 



Lower jaw. 



Length 2 4 2 2\ 



Width at condyles 1 8 1 4^ 



of back part of them Oil 010 



III. Arctopithecus. Bradypus, sp. Rilppell ; Pr. Max. ; 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. lUust. 

 t. 70. f. 1 a. Wiedemann, Arch. Zool. und Zoot. i. t. 1 and 1*, and 

 SpLx, Cephal. t. 7. f. 12, figure the skull, and Blaiuville 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 mdividuals of this genus as belonging to one species, and have 

 given an indefinite description, so as to include them. Cuvier (Reg. 

 Anim. ed. 1. 217) thus describes that species : " Sa couleur est grise, 

 souvent tachetee sur le dos de brun et de blanc : plusieurs individus 

 portent entre les epaules une tache d'un fauve vif que traverse une ligne 

 longitudinale." He refers for the species to both Bvfon's figures, 

 xiii. t. 5 & 6. In the second edition he remarks, "On connait un 

 Ai dit la dos briile, parce qu'il a entre les epaules une tache noire en- 



