164 ME. n. G. SEELEY ON bSSFOUS EESEMBLANCES 



the outer side ; but the distal articulation is not so pulley -like, nor 

 so deeply cut, iu Crocodiles. 



The tibia of the Crocodile is unlike that of the bird at both 

 the proximal and distal ends. The proximal end in birds deve- 

 lops a considerable forward cnemial process ; and at the distal 

 end the Crocodile has no condyles like those of the bird. 



A-t its proximal end the bird's fibula is usually very similar to 

 that of the Crocodile, while it very rarely happens that the bird's 

 fibula is prolonged to the distal end of the tibia (as iu certain fowl), 

 and then it is so attenuated that the shaft and distal end are not 

 comparable to those of the Crocodile. 



The tarsus of the Crocodile is in no way comparable with 

 that of birds. 



Even in the Penguin, where the bones usually named meta- 

 tarsals are applied to the ground, they are still anchylosed to- 

 gether, and three in number, instead of four as in Ci'oeodiles. 

 The outside toe is the largest in birds and has most phalanges in 

 the digit, while in Crocodiles the inside metacarpal is the stoutest, 

 and has fewest phalanges. 



The claw- phalanges are very similar in form in birds and 

 Crocodiles ; and a similar groove runs along each side of the 

 bone. 



Birds differ from Crocodiles in not having cervical ribs ; the 

 dorsal ribs of birds consist of only two pieces, both ossified, 

 between the sternum and vertebrae, while in the Crocodile there 

 are four elements, of which the proximal one only is fully ossified. 

 The lateral ossifications of the. bird's ribs are represented in 

 Crocodiles by small cartilaginous processes. In birds the anterior 

 head of the rib alw^ays articulates with the centrum, while in the 

 true dorsal ribs of the Crocodile both heads articulate with the 

 transverse process. 



§ 3. The Chameleon-cJiaj'acters of the Crocodile. 



The bones of the skull in the Chameleon are thin or represented 

 by membranes, and thus are generally unlike the massive bones of 

 the Crocodile ; moreover the difference in size probably obscures 

 some similitudes as well as some differences. 



From the prolongation backward of the parietal and squamosals 

 the skull has enormous perforations to represent the small tem- 

 poral fossae of the Crocodile. On the muscular mechanism which 



