in. EXTINCT SPECIES OF AMEEICAN OX. 15 



The process formed by the conjunction of the temporal, sphenoidal, and frontal 

 bones, at the inferior limit of the temporal fossa, is very much larger and more 

 prominent than in the Bison. 



The supra-orbitar foramen is placed about twenty lines within the supra-orbital 

 margin. 



The temporal fossa (Plate IV., Fig. 1), is relatively more superficial than in the 

 Bison, but is more oblique in its course forwards and downwards, and has a 

 greater breadth from the base of the horn-core to the root of the zygoma. 



Admeasurements. 



Prom middle line of os frontis to the tip of the horn- 

 core above . . . . . . .16 inches, 6 lines. 



Length of posterior curve of horn-core . . 15 " 6 " 



Greatest distance between the bases of the horn-cores 



above 5 " 6 " 



Antero-posterior diameter of base of horn-cores . 4 " 6 " 



Vertical " " . . 3 " 



Circumference at base . 12 " 6 " 



" three inches from the base above . 10 " 



Greatest breadth of head at the supra-orbitar margins 9 " 6 " 



From occipital condyle to the lachrymal margin of 



the orbit 11 " 



Height from basilar process to summit of frontal 



process at the inion ...... 9 " 



Breadth at the glenoid articulations . . . 8 " 6 



Length of temporal fossa . . . . 6 " 6 " 



The specimen of the cranium of an extinct ox, described by Dr. De Kay, before 

 referred to, without doubt belongs to the Bootherium cavi/rons. From its muti- 

 lated condition, the concavity of the frontal process was suspected as being the 

 result of the removal of the whole of the external plate of the os frontis, and the 

 species was supposed to be the same as that indicated by two heads described by 

 Pallas, 1 and one by Ozeretskovsky. 2 



One of the specimens of Pallas was discovered on the shores of the Ob, imme- 

 diately under the arctic circle; the other was found more northerly in the region 

 of Tundra. That described by Ozeretskovsky was obtained at the mouth of the 

 Yana, between the Lena and Indigirska. 



In the better specimen of those indicated by Pallas, Cuvier 3 says the forehead is 

 flat,' and the bases of the horn-cores occupy all the space from the orbits to the 

 occipital crest, and approach on a straight line, leaving not more than a finger's 



1 Nov. Com. Petrop. xvii. p. 601; Nov. Act. Petrop. i. 2, p. 243. 

 a Me'm. de 1'Acad. de St. Petersburg (1810), iii. p. 215, tab. 6. 

 3 Ossem. Fos. ed. 4, t. vi. p. 313. 



