CROCODILIA. 45 



base, especially the hinder pair, where the base fills up the entire interval between the 

 articular surface and the base of the spine (see fig. 2). There is the usual deep exca- 

 vation at the fore and back part of the base of the spine (ns) for the insertion of the 

 interspinal ligaments. The neural spine is compressed, moderately long, straight and 

 truncate at its summit. 



Although the hypapophysis maintains its characteristic form with much constancy 

 in the homologous vertebrae of the same species of Crocodile, it varies in different 

 cervical vertebras of the same individual in certain existing species. It is, for example, 

 shorter and thicker in the third and fourth vertebras than in the succeeding ones in the 

 Crocodilus acutus ; whilst in the Crocodilus biporcatus the hypapophysis of the third 

 cervical is more compressed than that of the sixth. The greatest difference is, how- 

 ever, presented, as far as I have yet made the comparison, by the cervical vertebras of 

 the Alligator lucius, in respect of the hypapophysis, which is broad and short in the 

 third and fourth cervicals, but becomes long and slender in the succeeding cervicals. 

 The small vertebral centrum (fig. 4, T. IX) resembles, in its broad and stunted 

 hypapophysis, that of the third cervical vertebra of the Alligator, but with an indication 

 of a median rising and lateral depressions, behind that process, like those which are 

 more decisively shown in the fifth cervical vertebra of the larger individual of the Croco- 

 dilus Hastingsia, to which species I believe the specimen fig. 4 to belong. It is the 

 homologous vertebra with fig. 8, T. V, and w r ell illustrates the different proportions 

 of the bones in different species of Crocodile. 



Fig. 6 gives a view of the anterior surface of the first sacral vertebra of the 

 Crocodilus Hastingsia : the under surface of the centrum has ceased to develope the 

 median ridge ; the short and thick ribs (pi) have completely coalesced with both the 

 centrum and neural arch. The anterior concavity has a fuller and more exact elliptical 

 form than that of the Crocodilus toliapicus (fig. 5, T. V) ; the anterior zygapophyses 

 do not project over the rim of that concavity; but, like those of the Alligator and 

 Crocodile, they are more transversely extended than in the Gavial. 



The general proportions of the first caudal vertebra (fig. 7, T. IX) are intermediate 

 between those of the Crocodilus toliapicus (fig. 7, T. IV) and of the Crocodilus champsoides 

 (fig. 10, T. V) : the under surface of the centrum is fiat, not concave, lengthwise, as 

 in both the Sheppy Crocodiles ; the side of the centrum is irregularly tuberculate, not 

 smooth, and concave lengthwise; the broad and high neural spine is deeply grooved at its 

 fore part : a smaller proportion of the hinder end of the centrum (fig. 5) is occupied by 

 the articular ball than we find in the antecedent vertebras. 



As none of the other numerous vertebras and portions of vertebras give any indi- 

 cations of a different species from the Crocodilus Hastingsice, or add any material 

 characters to those of that species which have been deduced from the parts of the 

 skeleton already described, I refrain from trespassing on the reader's attention or 

 occupying further space by their description or figures. 



