190 



REPORT — 1846. 



Fig. 8. 



Partly disarticulated cranium of a young ostrich {Struthio camelus), natural size. 



found distinctly perforating the middle of its lower border (fig. 8, 6, tr). The 

 alisphenoid is deeply impressed by the chief ganglions of the mesencephalon, 

 viz. the optic lobes. The prosencephalon or hemispheres are' still defended 

 principally by expanded parietals (ib.7^) and frontals (ib. n)*. 



In the crocodile these spinal elements of the cranium are much restricted 

 in their development, and a larger proportion of the hemispheres is defended 

 by the orbitosphenoid (fig. 9, 10), which here surpasses the alisphenoid (ib. e) 

 in size. This, however, still performs its essential and characteristic func- 



Fi£. 9. 



Vertical longitudinal section of the cranium of a crocodile (Crocodilus acutus). 



tions of protecting the sides of the mesencephalon, and giving issue to the 

 chief part of the trigeminal nerve. Owing to the diminution in size of the 



* The right frontal has been removed to show better the extent and connections of the 

 orbitosphenoid (10) and the prefrontal (14). 



