114 The Rev. W. D. Conybeare's Additional Notices 



be obsei'ved on either side the post-orbital part of the head * ; that is to sav% 

 an upper fossa^ included between the parietal bone (m), the post-orbital part 

 of the frontal (h'), and the part of the temporal (marked n), which from its 

 analogies I should wish to designate as the squamoso-zygomatic bone ; and a 

 lower fossa immediately beneath the firsts included between the post-orbital 

 process of the frontal (h"), and the post-orbital process of the jugal(c); the 

 portion of the temporal which surrounds the cavity of the tympanum and car- 

 ries the condyle of articulation with the lower jaw^ answering to the os Quadra- 

 turn of birds (o) ; and another bone (marked p), interposed between the last 

 and the jugal, and considered as ajiother dismemberment of the temporal. 



I am obliged to recur to these circumstances, because much confusion has 

 existed with regard to these two fossae ; the lower fossa having been consi- 

 dered as the true temporal fossa, and the upper as peculiar to the crocodile ; 

 whereas in fact the reverse is rather the true representation of the case. 



The upper fossae are undoubtedly the true temporal fossae. A comparison 

 with the temporal fossae of the other lacertee will at once prove this, for both 

 are included by the very same bones ; namely, the parietal, posterior frontal, 

 and the squamoso-zygomatic portion of the temporal : the upper branches of 

 the temporal muscle are also attached round the edges of this fossa. 



There is much difference in the size of this upper fossa in different species 

 of crocodile. In the Crocodilus sclerops it does not exist at all, the space in 

 which it ought to occur being covered up by the extension of the contiguous 

 bones ; in the gavial, on the contrary, it is considerably larger than in other 

 speciesf . A friend, possessed of great anatomical knowledge, has pointed 

 out the true cause of this difference. The gavial, having a much longer lever 

 to move in its lower jaw than the other crocodiles, requires a stronger mus- 

 cular action. The temporal muscle, therefore, which is little employed in the 

 other species, and exists only as a rudiment, (its functions being supplied, as we 

 have already seen, by the masseter,) is in the gavial more developed, and con- 

 sequently the temporal fossae require and receive a greater extension. 



The lower fossae appear also to be subsidiary to the main or upper tem- 

 poral fossae, and, perhaps, are also connected with the attachment of branches 

 of the masseter ; but I have not seen a clear explanation of the attachment 

 of the muscles in this part. 



In the other lacertae there are no lower fossae ; but the contour of the part 



* I have again to acknowledge my obligations to a friend for many important observations on 

 those temporal fossae. 



t I spoak here of recent species : some fossil species of crocodile have this fossa still larger 

 than tlio recent gavial. 



