376 Annals of the Carnegie Museum. 



the pelvic fins, all smooth, and with only one spiniform projection, 

 without serrations. Neural spines in advance of the dorsal fin with 

 broad antero-lateral expansions, as in the type species. Scales of the 

 flank thin, in most cases poorly preserved. 



This species is represented in the collection by a number of more or 

 less incomplete individuals, the better preserved of which are shown 

 slightly reduced in size in Plates XXIII and XXIV, fig. 2. A com- 

 posite drawing or restoration has not been attempted, but it is evident 

 that an understanding of all the characters can only be gained by a 

 synthesis of details exhibited by a number of fragmentary specimens. 

 One must also be careful not to be misled by deceptive appearances, 

 due to accident, or conditions of preservation. For instance, owing 

 to weathering, or the effects of chemical action, the number of ribs 

 and fin-rays sometimes appears to be larger than is natural, they 

 having been split up. This condition is faithfully represented in 

 respect to the dorsal fin-rays and anterior neural spines of the speci- 

 men shown in Plate XXIII, fig. 1. A similar splitting of the ribs, 

 haemal spines, and fin-supports is often observable in fishes from the 

 Green River shales and elsewhere. 



Diplomystus sp. ind. 



A second Clupeoid species, probably of Diplomystus, but much 

 smaller than that already described and of inferior preservation, is 

 indicated by a number of crushed and otherwise distorted individuals, 

 the total length of which does not exceed five or six centimeters. Very 

 likely they are the fry of some larger form at present unknown, but 

 differing from D. goodi in the lesser depth of the abdominal region. 

 Their present condition does not, however, permit anything like an 

 adequate description. 



The manner in which the outline of the body is deformed in these 

 fishes, a process which has sometimes been called " telescoping," 

 suggests a slow current in the waters while sedimentation was in 

 progress. Similar appearances are common in various Mesozoic and 

 other horizons, especially in the Triassic sandstones of eastern North 

 America, where the rock-making materials are supposed to have been 

 laid down in shallow estuaries or brackish-water embayments partially 

 cut off from the sea. It has not been thought worth while to illustrate 

 these much dilapidated fish-remains. 



