266 G. F. Eaton — Collection of Tr lassie Fishes at Yale. 



easily distinguished from other species by the peculiar develop- 

 ment of the scales of the anterior dorsal ridge. Dr. Woodward 

 describes his type in the collection of the Geological Society of 

 London as follows : 



"A species attaining a length of about 0*2 [m]. Trunk 

 with a considerably arched dorsal border, the depth of the 

 caudal pedicle more than one-third as great as the maximum 

 depth of the abdominal region. Length of head with opercular 

 apparatus less than the maximum depth of the trunk, and con- 

 tained four times in the total length of the fish. Fins as in 

 S. fultus. Scales smooth and not serrated, those of the middle 

 of the flank in part twice as deep as broad ; dorsal ridge-scales 

 large and conspicuous, comparatively obtuse in large specimens. " 



To this may be added that the last scale of the anterior dorsal 

 ridge has its posterior end blunt and not produced, while the 

 scale on the ventral line immediately in front of the anal fin 

 has its posterior end notched. The ribs are more strongly 

 developed than in other species. 



SemionotKS ovatus W. C. Redfield. 



Palceoniscus ovatus W. C. Bedneld, 1841, This Journal, vol, xli. 

 Ischypterus ovatus Sir P. Egerton, 1850, Quart. Jour. G-eol. Soc, vol. vi. 

 Ischypterus ovatus J. S. Newberry, 1888, Mon. U. S. Geol. Surv., No. xiv. 



Several specimens are to be found bearing this name, but, as far 

 as the writer can ascertain, only one, the type at Columbia 

 University, is so well preserved as to afford specific distinction. 

 The only character given hitherto in which this species differs 

 from others is the greater proportionate depth of body midway 

 between the head and dorsal fin. The type specimen, however, 

 shows another character which will probably be found more 

 reliable, viz., a greater number of dorsal and anal fin fulcra 

 than is fonnd in the other American species of this genus. 



S. ovatus, length 11 inches, depth 3f inches. 



Position and size of fins about the same as in S. fultus. 



Dorsal fin fulcra 21, actually preserved. 



Anal fin fulcra 19, actually preserved. 



Apparently 5 dorsal fin fulcra originate on the dorsal line, 

 and the 6th is equal in length to a little less than one-half the 

 anterior margin of the fin ( Plate YI, fig. 5). 



There is much confusion about the localities ascribed to the 

 American species of Semionotus. For example, the two imper- 

 fect specimens to which Agassiz applied the name 8. fultus 

 were found at Sunderland, Massachusetts, and specimens in 

 the Redfield Collection, whose original labels were 8. fultus, 

 have proved to be 8. tenuiceps from Massachusetts and 8. 



