ISOSPONDYLI. IT 



Measurements. 



u. 



Total length 090- 



Length (axial) to below D. 1 038 



Length (axial) to above A. 1 043 



Length (axial) to base of caudal fin 070 



Length of head 022 



Depth at orbit OIT 



Depth at pectoral fin 026 



Depth at dorsal fin 024 



Depth at caudal peduncle 008 



r 



This species is represented by several specimens, from Twin Creek 

 Wyoming. 



DiPLOMYSTUS THETA Cope. 



Bulletin U. S. Geol. Surv. Terrs., 1877, p. 811. Clupea iheta Cope, Annual Report U. S. Geol. Surv. 



Terrs., 1873, p. 461. 



Represented by a specimen from the Green River shales near the mouth 

 of Labarge Creek, in the upper valley of Green River. It is a larger species 

 than the C. Immilis Leidy, which is also found at the same locality, and it has 

 much longer anal fin. Its radii number 26, possibly a few more, as the end 

 appears to have been injured. The dorsal fin is short; the last ray in 

 advance of the line of the first of the anal. The body is deep. Number 

 of vertebrae fi-om the first interneural spine to the last interhsemal, 29. Depth 

 at first dorsal ray, .04«5; depth at last anal ray, .0170; length of 29 ver^ 

 tebrae, .0780. 



The posterior part of the body having been lost, the number of anal 

 rays is unknown. It is quite possible that further investigation may show 

 that the -D. analis is identical with this species. 



DiPLOMYSTUS HUMiLis Leidy. 



Proceed. Acad. Phila., 1856, p. 256. Final Report U. S. Geol. Surv. Terrs, i., p. 195, Plate xvii, fig. 1. 

 Clupea 2>wiUa Cope, Proceed. Amer. Philos. Soc, 1870, p. 382. Annual Report U. S. Geol. Surv. 

 TeiTS., 1870, p. 429. 



Plate rx, fig. 8; Plate X, fig. 4. 



This and the following species, already referred to a distinct section of 

 the genus Liplomystus, difi'er from those above described in several points. 

 They have a much shorter anal fin, and the caudal part of the vertebral 

 column is thus shorter. The anterior neural spines do not present the 

 antero-posterior laminar expansion. The ventral fin commences a little 



