126 



the specimens we have referred to two named species. Professor Marsh 

 subsequently named, five species from remains obtained in the same locali- 

 ties during his exploration of 1870. Professor Cope has more recently named 

 four additional species. It is probable that when the fossils are more care- 

 fully studied, the number of species to which they have been referred will 

 be reduced. 



CeoCodilus aptus. 



This species was originally named in 1869 from a fossil preserved in the 

 Geological Cabinet of the General Land-Office in Washington. The speci- 

 men was obtained by Colonel John H. Knight, United States Army, near 

 South Bitter Creek, Wyoming. Though consisting of a detached vertebra, it 

 especially attracted my attention from having previously seen no remains of 

 crocodiles in the large collections of fossils from the Tertiary formations of the 

 west. 



The vertebra represented in Fig. 2, Plate VIII, belongs to the cervical 

 series, and resembles, both in size and form, the sixth or seventh of the Mis- 

 sissippi alligator. The bone appears to have been of mature age, and seems 

 thoroughly petrified. It has lost the greater part of its neural arch and 

 dependent processes, but is otherwise well preserved. From portions of 

 adherent matrix, it has been imbedded in a soft rock similar to that adherent 

 to some of the bones from other localities above mentioned. 



The body of the bone in its axis is 16 lines long; its height and breadth 

 in front are 14 lines. The hypopophysis, directed obliquely downward and 

 forward, as in the alligator, is about 5 lines long. Back of the process the 

 body is less prominently carinated than in the latter animal. 



Ceocodilus Elliotti. 



The species thus named was originally designated from a specimen 

 obtained, during Professor Hay den's exploration of 1870, at the junction 

 of the Big Sandy and Green Rivers. It consists of an upper-jaw fragment 

 containing two* teeth and portions of two others, and is represented in Fig. 4, 

 Plate VIII. It appears to be the anterior portion of the left maxillary, con- 

 taining the fourth and fifth maxillary teeth and the fangs of the two succeed- 

 ing ones. The shape of the jaw-fragment is nearly like that of the corre- 

 sponding portion of the upper jaw in the mugger {Crocodilus palustris) of 

 India, but is more rugose on its exterior surface, and the palatine surface is 



