398 C. R. EASTMAN — JURASSIC FISHES FROM BLACK HILLS 



todus guentheri Marsh '•' and C. robvslns Knight,"!" are the only recognizable 

 forms which have been discovered up to the present time. These species 

 are from the Upper Jura of Wyoming and Colorado, but aside from their 

 evidence as to the widespread distribution of the genus are without 

 special significance. 



In view of these circumstances, very great interest attaches itself to 

 the discovery by Mr N. H. Darton, in strata determined by him to be 

 basal Jurivssic, of several complete fishes which admit of detailed com- 

 parison with other forms, and furnish corroborative evidence as to the 

 age of the horizon. Mr Darton first announced his discover}'^ at the 

 winter meeting of the Geological Society of America in New York last 

 December,and contributed at the same time a brief account of the stratig- 

 raphy of the region. About a dozen, specimens were exhibited, all from 

 a locality three-quarters of a mile southeast of Hot Springs, South Dakota. 

 Later the material was generously placed in the hands of the writer for 

 investigation, and although a brief summary of the results was read be- 

 fore the Boston Society of Natural History in March of this year, the 

 details were withheld in order that they might appear in conjunction 

 with Mr Barton's published account of the geology of the Black Hills 

 district. Another reason for the dela.y was the hope of more perfect 

 material being discovered during field work of the present summer; un- 

 fortunately, however, this anticipation was not realized. 



The only other descriptions of fossil fishes from the Black Hills region 

 are those contributed b}'' Cope'l in 1891, the horizon being doubtfull}^ in- 

 terpreted on the evidence of the fishes themselves as Oligocene. These, 

 na.turally, are foreign to the present subject. 



Descripteon op the more perfect Fossils, 



Pholidophorus amerlcanus E. (plates 45-47) 



"Gracefully fusiform, upwards of 15 centimeters long, the head forming al)out 

 one-fourth the total length and slightly less than maximum depth of trunk, dorsal 

 arising behind pelvic tins; scales not serrated, smooth, nearly rhomboidal, over- 

 lapping ; flank-scales not especially deepened, several series of ventral scales finely 

 divided." ^ 



The specific characters were summarized as above in a paper read 

 before the Boston Society of Natural History, an abstract of which ap- 

 peared in Science^ for May 5, 1899. The association with Fholidophonis 



*Amer. Jour. Sci. [:i], vol. xv, 1878, p. 7G, woodcut. 



fibid. [4], vol. V, 1898, p. 186, figs. 1 and 2. 



J Amer. Naturalist, vol. .\xv, 1891, pp. G54-GoS ; Proc. Amer. A.«soc. Adv. Sci., vol. xl, 1891, p. 205. 



g Vol. ix, 1899, p. 042. 



