282 PROCEEDINGS OF THE NATIONAL MV8EUM. vol.52. 



Family SEMIONOTIDAE Woodward. 



A study of the characters of this family shows that the genera in- 

 cluded under it are fully developed Protospondyli, that is to say, 

 they belong clearly to that large group of "ganoid" fishes which 

 floui-ished chiefly during the Triassic and Jurassic periods, but de- 

 chned rapidly, and is represented at the present day by only two 

 fresh-water genera, Lepidosteus and Amia. From what ancient 

 stock the Semionotidae and other Protospondli are descended we 

 do not precisely know, but it may reasonably be inferred that the 

 late Palaeozoic forermmers {AcentropTiorus^eiQ,.) of the higher suborder 

 were derived from a modified type of chondrostcan. Beyond this, 

 when we inquire as to the origin of the Chondrostei themselves, we 

 find but few facts for our enlightenment. Their origm is at least as 

 ancient as that of the "fringe-finned ganoids," but there is as yet no 

 evidence of a genetic connection between the Chondrostei and cross- 

 opterygians. Enough, however, has been ascertained to show that 

 already in the Trias tmd probably even earlier the divergence between 

 chondrosteans and Protospondyli was strongly marked. 



SEMIONOTUS ELEGANS (Newberry). 



Plate 15, fig. 3. 



Ischypterus elegans Newberry, Monogr. U. S. Geol. Surv., vol. 14, 1888, p. 37, 



pi. 7, fig. 2; pi. 10, fig. 1; pi. 14, figs. 1, 2. 

 Ischypterus viodestus Newberry, Monogr. U. S. Geol. Surv., vol. 14, 1888, p. 38, 



pi. 9, figs. 1, 3. 



The original specimens serving for the establishment of this species 

 are now preserved in the American Museum of Natural History in 

 New York. They are nearly complete fishes, but much crushed, and 

 in becoming flattened their characteristic features have become ob- 

 scured. A large-sized specimen, 17 cm. in total length, and more 

 perfectly preserved than any other example of this species seen by 

 the writer, is contained m the United States National Museum col- 

 lection (Cat. No. 8109). It is from the Trias of Boonton, New Jersey, 

 and represented in my plate 15, figure 3. 



Genus LEPIDOTUS Agassiz. 



Syn. Prolepidotus Michael. 



Numerous species of this genus have been described, but many are 

 imperfectly known. No indications of the genus have yet been re- 

 ported from this country, with the exception of certain isolated 

 scales from the Kiowa shales (Cretaceous) of Kansas. The following 

 new species is regarded as standing in close relations with L. gallineki 

 (Michael), from the Rhaetic of Upper Silesia. 



