174 Mil, H. O. SEELEY ON OSSEOUS RESEMBLANCES 



phalanges in Emydians are not dissimilar ; only with them all the 

 digits terminate in claws, and the metacarpal bone of the fifth 

 finger is the stoutest. 



There is very little in common in the pelvis, which in Chelonians 

 is more like Lizards' than Crocodiles'. 



The femur is a stronger bone in Chelonians, with a large hemi- 

 spherical instead of a compressed subovate articular head. It 

 might be considered to diverge from the Crocodile's more than 

 Lizards', since the trochanteroid ridge which is developed behind 

 the head of the bone in Lizards may here he regarded as greatly 

 expanded from side to side, so as to produce an enormous tro- 

 chanter ; and to this modification the Crocodile ofiers no analogy. 



The tibia and fibula have a general resemblance, except that in 

 Chelonians they are stouter, and difi'er a little in their distal ar- 

 ticulations. 



The OS calcis and astragalus of Testudines are anchylosed to- 

 gether, and show nothing like the Crocodilian form. The distal 

 row of bones is more numerous than in Crocodiles. 



In reducing the digits of the hind foot to four, Testudo becomes 

 Crocodilian ; and, as in Crocodiles, the hind foot is more elongated 

 than the fore foot, though not to the same extent. 



§ 7. The Ophidian Characters of Crocodiles. 



The resemblances of Serpents to Crocodiles are necessarily 

 limited to the skull and vertebral column. Like Alligators, ser- 

 pents have the nostril divided by the nasal and premaxillary 

 bones ; but the premaxillary is single and toothless. Almost 

 every other character gives matter for distinction ; in the poison- 

 ous group the divergence is least, from both frontal and parietal 

 bones being single. 



In the vertebral column the resemblance is limited to the pro- 

 eoelous articulation of the centrum and the compressed subquadrate 

 neural spine, 



§ 8. The Urodelcm Characters of Crocodiles. 



No skull of a living Amphibian is likely to be mistaken for 

 that of a Crocodile. The nasal sac is surrounded by premaxil- 

 lary, maxillary, nasal, and vomerine bones. As in Monitor, 

 neither orbit nor orbital fossa is circumscribed by bone. As in 

 fishes, an enormous parasphenoid covers much of the base of the 



