422 GEOLOGICAL SURVEY OF THE TERRITORIES. 



acteristic of Sauroceplialus or Saurodon leanus, as pointed out by Harlan 

 and Hays. The vertebrae form a series of 13.4 inches in length, embrac- 

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

 the inferior pits and inserted pleurapophyses, and absence of lateral 

 grooves. There are important differences from what has been described 

 as characteristic of Saurocephalw. The neural arches, whose bases only 

 are preserved, 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 case at least to be coossified. 

 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. 



M. 



Length of maxillary bone 0. 158 



Depth at condyle .. 031 



Depth at extremity 022 



Length of crown of a tooth 0061 



Diameter of crown at base- 0038 



Length of alveolar border of dentary 106 



Depth of symphysis border of dentary 047 



Length of opecular condyle 018 



Length of centrum anterior caudal 024 



Width of centrum, (crushed) , 0278 



Depth of centrum, (crushed) . 047 



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

 fork of Smoky Hill Eiver, near its mouth. ♦ 



GENERAL CONSIDERATIONS. 



There have been described above remains of three species, which 

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

 cases' the jaws and teeth were found together; in the third tbey came 

 in the same small box without special indication of locality; but the 

 vertebrae are of precisely the same size, sculpture, mineralization, and 

 color, as a large series whose locality is exactly known, to which they 

 probably belong. Moreover, the jaws and vertebrae- bear the same rela- 

 tion of size to each other in all three series. These facts render it highly 

 probable that the remains are in each case rightly referred to the same 

 animal. That no mixture has occurred is also probable from the fact 

 that the large and small series (Ichthyodectes and 8. prognafkus) came from 

 the same locality, (Sheridan,) while the species of intermediate size was 

 discovered one hundred and sixty miles from the mouth of the Solomon 

 Eiver, a long distance off. The pectoral spine, accompanying and be- 

 longing to the S. prognatkus, I have shown to be the same as the Xipliac- 

 tinus of Leidy, but probably not of the species X. audax. 



The fourth series described above as 8. thaumas exhibits precisely the 

 vertebral characters of the two other species of Saurocephalus and I 

 cannot resist the evidence that it belongs to that genus or the same 

 family. Its remains pertain to one animal, as asserted by Professor 

 Mudge, and their color and condition, coated with a chalky deposit of 

 • a ferruginous yellow color, lend great probability to the statement, to 

 say nothing of more important reasons. ISTo remains of pectoral spine 

 are preserved ; but instead, the remarkable segmented ray described. 

 This comes from the posterior region of the vertebral column, and con- 



