Cope.] obi [Dec ^5^ 



The cerebellum is larger than a single hemisphere. Its superior surface 

 is somewhat flattened, and descends forwards ; the lateral boundary of 

 this face is a projecting edge which rises behind to an angle of the vermis. 

 The posterior face is shorter than the superior, and is vertical. It is sepa- 

 rated by a space trom a very prominent lateral convolution, while the 

 region of the flocculus is concave from the internal form of the ascending 

 portion of the petrous bone. This concavity is open anteriorly. The 

 base of the fifth pair of nerves is below its apex, and that of the sixth 

 below the inferior extremity of the lateral convolution. The section of the 

 medulla oblongata is a transverse oval ; its inferior face and that of the 

 pons varolii, smooth. A deep fossa just anterior to the bases of the optic 



Measurements of brain. M. 



Length from vermis to olfactory lobes inclusive 070 



" of olfactory lobes from above 015 



" of hemispheres, from above . ." 030 



" of cerebellum from above 034 



Depth of olfactory lobe 010 



" of hemisphere 033 



" of cerebellum and medulla 036 



" of medulla at vermis 015 



Width of olfactory lobes at middle 030 



' ' of hemispheres in front 044 



behind 044 



" of cerebellum 036 



" medulla at vermis 030 



PERIPTYCHUS RHABDODON Cope. 



I have obtained a cast of the top and sides of the cerebral hemispheres, 

 and the proximal portion of the olfactor}^ lobes, from a skull of a Periptychus 

 in which the teeth are preserved, and prove the species to be the P. r7iab- 

 dodon. The olfactory lobes are enormous, and the hemispheres small and 

 very flat. The mesencephalon is entirely exposed. The cerebral hemispheres 

 are very flat, and are only differentiated from the olfactory lobes, by a 

 moderate contraction and depression, which forms the peduncle of the 

 latter. Only the proximal part of the olfactory lobes is preserved, but this 

 expands so as to be only a little narrower than the hemispheres. The 

 peduncle has a ridge on the median line, and a shallow fossa on each side 

 of it. The lateral outlines of the hemispheres diverge, and the widest part 

 is posterior. There is no indication of sylvian fissure. The transverse sec- 

 tion of the hemispheres would be a flat arch, but for the presence of a 

 longitudinal oval protuberance on each of them, which do not quite touch 

 the median line, and which have definite boundaries. If tlieir limits 

 determine the size of the cerebral hemispheres, then the latter are wider 



