336 On Fossil Quad?'umana. [Oct. 



of one side, of a quadrumanous animal belonging to a much larger species 

 than the bone we found. 



Our fossil is the specimen which accompanies this communication. It 

 is the astragalus of a right hind leg. It is completely mineralized, 

 having a specific gravity of about 2^8, and it appears to be impregnated 

 with hydrate of iron. Although but a solitary bone of the foot, the re- 

 lations of structure are so fixed that the identity of the fossil is as cer- 

 tain as if the entire skeleton were before us. The very shallow excava- 

 tion of the superior surface for the pulley-like articulation with the tibia ; 

 the form and extent of the lateral articulating surfaces for the external 

 and internal malleoli ; the considerable elongation of the apophysis for 

 the head and neck of the bone ; the slight obliquity with which it is sent 

 off from the body ; and the diagonal direction and form of the principal 

 articulating surface with the calcaneum, are charricfers which, taken in 

 conjunction, incontestably prove that the fossil is a quadrumanous astra- 

 galus. It would be needless, therefore, to dwell on the points of differ- 

 ence between it and the astragali of those orders of Mammalia which 

 have an allied form. It is only requisite to ascertain how it agrees with 

 the corresponding bone in exis ling species of Quadrumana. It closely 

 resembles, in size and general form, the astragalus of the Semnopithecus 

 Entellus^ which we send along with the fossil for comparison. 



The principal dimensions are as follow-: — 



Dimentions. -Sewalik Fossil Monkey. SemnopitTiecus Eniellus. 



Extreme length of astragalus 1-3 inch 1*35 inch. 



Extreme width of body of astragalus.... 1* 1-03 — — 



Length of body OS 0-85 



Greatest diameter of navicular head.... 0-65 0 65 



Thickness of ditto , 0 45 ■ 0-5 — 



The chief peculiarities of the fossil astragalus, compared with that of 

 the Entellus, are these : — The upper articulating surface for the tibia 

 is more convex than in the Entellus, and less square in the outline, the 

 lateral margins approximating as they run backwards ; the outer one 

 being also more elevated. The peroneal articulation is precisely of 

 the same furm and extent as in the Entellus ; and the rough fossa be- 

 tween it and the large calcanean surface also corresponds. The articu- 

 lar surface for the inner malleolus somewhat differs : in the fossil it is 

 long, shallow, and rather pyriform in outline, while in the Entellus it is 

 cup-shaped, deeper, and more extensive. The other pits and inequa- 

 lities of the inner side correspond ; but the entire surface slopes off 

 more obliquely ia the fossil. The great calcanean surface has the same 



