Cope,] ^'^ -^ [Nov. IS, 1870. 



same small box witliout special indication of locality ; but the vertebrfe 

 are of precisely the same size sculpture, mineralizatiou, and color as a 

 large series whose locality is exactly known, to which they probably 

 belong. Moreover, the jaws and vertebrae bear the same relation 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 j)robable from the facfe that the 

 lai-ge and small series (Ichthyodectes and S. proguathus) came from the 

 same locality (Sheridan), while the £i)ecies of intermediate size was dis- 

 covered 160 miles from the mouth of the Solomon river, a long distance 

 off. The pectoral spine, accompanying and belonging to the S. prog- 

 nathus, I have shown to be the same as the Siphactinus of Leidy, but 

 probably not of the species X. audax. 



The fourth series described a,bove as 8. tliaumas 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 Prof. Mudge, 

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

 yellow color, lends great probability to the statement, to say nothing of 

 more important reasons. ls"o remains of pectoral spine are jpreserved ; 

 but instead, the remarka,ble segmented ray described. This comes fi'om 

 the posterior region of the vertebral column, and is, I believe, an anal 

 spine, or the adjacent rays or compound ray forming the margin cf the 

 caudal fin. This finds support in the analogous structures already men- 

 tioned as occurring among Siluroids, etc., and the resemblance cf the 

 pectoral spine to the same weapon of the same grouT) adds to the proba- 

 bility of the correctness of this conclusion. 



These remarks are made because Prof. Agassiz, in the Poissons Fos- 

 siles, has referred several spines to the Cestraciont genus, Ptychodus, 

 wliich are very similar in character to that described above as the anal or 

 caudal support of Saurocephalus thaumas. These were derived from the 

 up]per cretaceous chalk of Kent, England, where Ptychodus teeth also oc- 

 cur. The Saurocephalus teeth, described by Prof. Agassiz in the same work, 

 were, however, derived from the same chalk and the same locality, and, 

 from what has psreceded, I believe the segmented spines should be 

 referred to the latter genus rather than to Ptychodus. This is the more 

 probable, in view of the fact that Prof. Mudge did not procure a single 

 Ptychodus tooth during his exploration. 



ON THE FISHES OF A FEESH AVATER TERTIAPY IN IDAHO, 

 DISCOVERED BY CAPT. CLARENCE KING. 



By E. D. Cope. 



The materials on which the present accouiit is based were placed in 



my hands by the Smithsonian Institution. They were obtained by Capt. 



Clarence King, on his expedition sent out by the Government, for the 



geological exploration of the fortieth parallel west of the Mississippi river. 



