1S70.] '^'J ' [Cope. 



broad obtuse and thinned extremity. Its superior margin is marked with 

 one or more acute ridges, whicli look as tbougii it bad a contact with a 

 large preorbital bone. Two fractured bones with an elongate reniform 

 condyle on a wide peduncle, look like the articular extremity of an opei'- 

 culum, which view is confirmed by their application, to some flat, coarsely 

 rugose bones wliich resemble parts of the latter. 



The dentary bone is remarkable for its straightness and laminar char- 

 acter, and for the depth of the symphysis. The length of the latter is 

 preserved, while posteriorly to it the lower margin of the dentary is 

 broken away. The alveolar margin is slightly concave, and unites with 

 the symphyseal at an angle of 65^. There are twenty-seven teeth and 

 alveolae, which grow a little larger to the posterior extremity of the 

 series ; anterioi'ly the alveoli are confluent externally, but posteriorly the 

 septa are frequently complete, though thin. In neither this bone nor the 

 maxillary are to be found the foramina along the bases of the teeth, cha- 

 racteristic of Saurocephalus or Saurodon leanus, as pointed out by Harlan 

 and Hays. The vertebrae form a series of 13 .4 inches in length, embracing 

 thirteen caudals. This is indicated by the close approximation of the 

 inferior pits and inserted pleurapophyses, and absence of lateral grooves. 

 There are imiDortant differences from what has been described as charac- 

 teristic of Saurocephalus . The neural arches, whose bases only are pre- 

 served, are much lighter and narrower than in it, and its sutural union 

 with the centrum is less distinct. Their bases issue from pits ; but their 

 anterior portions appear in some cases at least to be co-ossified. They 

 exhibit a longitudinal rib near one side. There are no heavy neural 

 spines preserved. The sides of the centra are longitudinally rugose 

 striate ; inferiorly they are rugose with exostoses. 



Measurements. 31. 



Length maxillary bone 0.158 



Depth at condyle 031 



" " extremity 023 



Length crown of a tooth 0061 



Diameter crown at base 0038 



Length alveolar border of dentary 106 



Depth symphysis " " 047 



Length opercular condyle 018 



Length centrum anterior caudal 024 



Width . " (crushed) 0278 



Depth " " 047 



Specimens from six miles south of Sheridan, Kansas, on the north fork 

 of the Smoky Hill river near its mouth. 



General Considekatioks. 

 There have been described above, remains of three species, whicli 

 include jaws with teeth, and associated vertebrae. In two of these cases 

 the jaws and teeth were found together; in the third they came in the 

 -'.. p. s.— VOL. xr— 40k 



