MK. T. ATTHEY ON PTEEOPLAX COKNTJTA. 181 



groove ; and in each runs a delicate rather obscure suture ; the 

 upper unites the so-called supraoccipitals to the exoccipitals, the 

 lower these latter bones to the quadrates. 



The true occipital is undistinguishable, and the basioccipital 

 probably absent. The height of the occipital surface near its 

 middle is three-tenths of an inch ; at its outer part at the base 

 of the horns, where the bones are very strong, and have been 

 able to resist pressure better than other parts, it is five-tenths of 

 an inch. 



Upper surface of the larger cranium. — This has not been figured. 

 Having been carefully cleared of the matrix it shows all the su- 

 tures ; but the bones are badly preserved and the pittings almost 

 all obliterated. The following are its dimensions : — from the 

 median line of the anterior broken end to the point of the epiotic 

 horns seven inches, from the same point along the median line 

 to the posterior edge of the occiput five inches and a half, from 

 the middle point of occipital border to point of left opiotic horn 

 one inch and a quarter, between the epiotic horns three inches 

 and nine-tenths. The breadth of the skull at the occipital mar- 

 gin three inches and six-tenths, over the posterior margin of the 

 parietals three inches and eight-tenths, between the posterior 

 points of the orbital curve three inches and four-tenths, between 

 the anterior points of the same one inch and seven-tenths ; the 

 breadth of the broken anterior end of the frontals is nearly one 

 inch. 



The right epiotic horn is broken off at the end ; otherwise the 

 outline of this cranium is on the whole nearly the same as that 

 of the smaller specimen ; it is rather broader, and perhaps be- 

 longed to an older animal : the frontals are worn as it were in 

 front; but the right side appears to have the normal length, 

 whilst the left is shortened. 



Under surface of the larger cranium (Plato XYI., fig. 1). — In 

 this the entire under surface of the cranial vault can be seen ; all 

 the parts below are gone ; the median suture of the vault through- 

 out with the parietal foramen is visible ; the palate, maxillary, 

 and premaxillary bones are wanting, and may have been more or 



