1887.] ^^'^ [Cope. 



Von Meyer in the B. kapfi,- and the posterior nostrils, which commence 

 in front of this union, have a much greater anteroposterior extent than in 

 that species. 



There is a fossa in the posterior part of the orbit which extends down- 

 wards and forwards. In the superior part of its fundus is the mouth 

 of a canal which extends from the pineal fossa of the brain case. I call 

 this the orbito-pineal canal. It will be again referred to in the description 

 of the brain. Below the anterior part of this fossa, and at the base of the 

 closed interorbital part of the brain-case, is the large optic foramen. It 

 looks outwards and forwards, and it is not certain that it is separated from 

 that of the other side by a septum. The lateral walls of the brain-case 

 are imperforate. There is no foramen for the trigeminus in the usual posi- 

 tion. A portion of the superior face of the sphenoid bone is split away, 

 and it may be supposed that the trigeminal foramen was at the base of the 

 brain on the line Avhere the lost portion joined the lateral walls. It must 

 have been of small size. A canal traverses the basioccipitalbone on each 

 side, commencing in conjunction with that of the opposite side, and ex- 

 tending outwards and backwards, and issuing on the suture joining the 

 basi- and exoccipital bones. 



Brain. The cast of the brain-case presents several peculiarities of im- 

 portance. The size is a little greater than that of an Alligator mississippiensis 

 Avhose skull slightly exceeds that of the Belodon buceros. Thus the dimen- 

 sions of the former are, length 500 mm., width at quadrates 290 mm.; of 

 the B. buceros, length 700 mm., width 240 mm. The distribution of parts 

 is different. The prosencephalon is relatively and absolutely smaller in 

 the Belodon, and the mesencephalon is larger. The epencephalon is not 

 very different in the two, and the contraction on each side of it is apparent 

 in the one as in the other. Posterior to it, the medulla is contracted to 

 a still smaller diameter in a manner not seen in the alligator. This region 

 is longer in the Belodon than in the latter. The brain proper is thus 

 bunched up or shorter and more elevated in the Belodon than in the alli- 

 gator. The contraction to the rhinencephalon is more abrupt in the Belo- 

 don. What gives the Belodon its especial character is the presence of an 

 enormous epiphysis. Tliis body is subquadrale in form, and occupies a 

 large fossa in the cranial roof, which is, however, not perforate. On each 

 side of the anterior portion a process extends outwards and forwards, 

 occupying a corresponding anteroposterior fossa in the cranial walls. The 

 process is continued, horn -like, on each side, and the cast forms a continuum 

 through the orbitopiueal canal to the orbit. Whether this represents a 

 nervous or arterial canal can only be surmised, but from the size of the 

 process of the epiphysis which enters it, I suspect that a nerve formed 

 part of its contents. There is no median distinction between the halves 

 of the prosencephalon and mesencephalon in tlie brain-case, thus resem- 

 bling other crocodiles. The mesencephalic bodies were probably lateral, 

 judging from the greater width of the cast below at the middle, as com- 



* Palffiontographica, Vol. viii. 



