206 FOSSIL REPTILES. 



diately at the external edge of this lachrymnal bone, and would 

 occupy all the space between the two lachrymals above the 

 nasal. It would descend into the bottom of the orbit to 

 articulate broadly to the palatine, and the anterior sphenoid ; 

 and in such genera as the quadrumana and ruminantia, which 

 have the frame of the orbit completely osseous, it would give 

 an apophysis behind, which would unite to the jugal to sur- 

 round the orbit. 



But this is not the case with the crocodile. There is, indeed, 

 a frontal bone, covering, as in the mammalia, the interval of the 

 orbits, furnishing a roof to them, or rather here, in consequence 

 of their direction, an internal border descending almost to the 

 root of the nasals. This bone even exhibits, in the individuals 

 just broken from the egg, a remain of a longitudinal suture, as 

 there is one in the mammalia, and which is speedily effaced. 

 But a suture, which never exists in the mammalia, and which 

 always, on the contrary, continues in the crocodile, separates 

 in front of the frontal on each side, a bone, which is thus 

 interposed between the lachrymal and the chief frontal, and 

 descends from the edge of the orbit to the root of the nasals. It 

 re-enters the orbit like the lachrymal, and descending lower, 

 there unites itself by an apophysis with the palatal bone. 



Between this apophysis and the palatal on one side, and the 

 maxillary on the other, and under the lachrymal, is a large 

 aperture which penetrates into the nasal cavity. It at once 

 fills the place of the sub- orbital canal, and of the pterygo-pala- 

 tine, and spheno-palatine foramina ; but it is especially filled, 

 in the fresh animal, by certain motive muscles of the lower 

 jaw, muscles which we shall find to be peculiar to the ovipara. 



The principal frontal bone does not descend into the orbit 

 under an osseous form, and all the space between it and the 

 palatine, as far as the sphenoid, or what may be called the inter- 

 orbital partition, is simply cartilaginous or membranous in the 

 fresh animal, which leaves it entirely vacant in the skeleton. 



Some traces of this arrangement are observable in certain of 



