1849.] OWEN ON FOSSIL REPTILES. 381 



which also a hypapophysis {hy) is developed from the under surface 

 of the centrum. 



The most marked difference between the vertebrae figs. 1 & 3 is 

 presented by the latter process : in fig. 1 it is double, or divided by 

 a median longitudinal cleft; in fig. 2 it is single, broad, flattened 

 and smooth below. These characters are well and accurately shown 

 in the figs. 2 & 4 of the inferior surface of the vertebrae selected. 

 A corresponcUng modification of the hypapophysis was presented by 

 other cervical and anterior dorsal vertebrae of each series respectively. 

 But the specific distinction of the two is manifested by other charac- 

 ters. The cer^dcal vertebra, figs. 3 & 4, is longer in proportion to 

 its breadth than figs. 1 & 2 : the parapophysis, p in fig. 1, comes 

 off from the middle of the side of the centrum : in fig. 3 its origin is 

 more advanced, and extends to the border of the anterior articular 

 cup. And these characters were not those distinguishing different 

 positions of the vertebrae in the same cervical series, any more than 

 those of the hypapophyses, but were characteristic of the other cer- 

 vical vertebrae of each series respectively. 



Two species therefore, of Crocodile or Alligator, were thus esta- 

 blished, equalling in size the existing Alligator lucius of the South- 

 ern States, or the Crocodilus acutus of Jamaica. 



Neither these, nor any other existing Crocodile of which I have 

 had the opportimity of examining and comparing the vertebrae, pre- 

 sents the same characters of the hypapophyses which have been de- 

 scribed and figured in the above fossil vertebrae. I regard the species, 

 therefore, to which these vertebrae respectively belonged as extinct, 

 and agreeably with actual knowledge, the oldest of the modern Cro- 

 codilian family. 



For the species characterized by vertebrae of the type of that depicted 

 in figs. 1 & 2, I propose the name of Crocodilus basijissus ; for the 

 species with the inferior process single, short and flattened, that of 

 Crocodilus hasitruncatus : these specific names refer, of course, to 

 the characters of the basal or inferior process (hypapophysis) : as 

 the names Lamna gracilis^ Otodus obliquuSy &c. relate, not to the 

 proportions or direction of the whole body of the sharks so-called, 

 but of that part which is most characteristic of the extinct species, 

 and most commonly found in the fossil state. It is interesting to 

 observe that the same kind of modification varies the hypapophyses 

 of the cervical centrums of these Crocodiles, as the corresponding 

 processes from the centrum of the last cranial vertebra of the reptiles 

 figured in figs. 6 & 7, PI. X. 



The proportions of the vertebrae of the Crocodilus basijissus re- 

 semble those of the vertebrae of the Alligator : the longer vertebrae 

 of the Crocodilus basitruncatus seem to me to have belonged rather 

 to a true Crocodile : in neither species are they so long and slender 

 as the corresponding vertebrae of the Gavials or long-nosed procaelian 

 Crocodiles. 



The vertebrae figs. 1-6, PI. XL, also appertain to the procaelian 

 type, and in the degree of the anterior concavity and posterior con- 

 vexity of the centrum most resemble the vertebrae of the Mosasaurus. 

 They arc, however, longer and more slender : the character of the 



2 D 2 



