86 The Sand Darter. [ February, 
of life commences at the close of the Cretaceous epoch and with- 
out any line of separation that can yet be detected continues on 
upward until only purely fresh-water forms are to be found. 
Dr. White, an eminent paleontologist and geologist, says that the 
line must be drawn somewhere between the Cretaceous and Ter- 
tiary epochs, but that it will be strictly arbitrary, as there is no 
well marked physical break to the summit of the Bridger Group. 
ea ae eee 
THE SAND DARTER. 
BY D. S. JORDAN AND H. E. COPELAND. 
E have often brought home with us a “ Johnny,” “ Speck,” 
or “ Crawl-a-bottom,” of a different type from any of those 
whose habits we already knew.! It had a very sharp nose that 
(Fie. 4.) THE SAND DARTER. 
projected over its mouth; its body was exceedingly slim and 
round, as transparent as jelly, but firm and wiry to the touch. 
Its belly and much of its back, after a fashion peculiar to itself, “ 
were quite bare of scales, and those along the sides were small 
and inconspicuous. These peculiarities seemed the more striking 
as the other darters are scaly, and, along the middle line of the 
belly especially, they are often covered with hard plates, an ar- 
rangement obviously adapted to their “ crawl-a-bottom ” habits. 
After much searching through the scattered and unsatisfac- 
tory descriptions which eastern naturalists have given us of the 
darters found in their bottles of alcohol, we decided that our 
little friend was the “pellucid darter,” or better, the “ sand 
darter ” (Pleurolepis pellucidus? Agassiz), for reasons soon to be 
given. 
1 American Naturalist, June, 1876. Page 33 
2 As this species is quite imperfectly ume te naturalists, we here ngoli its 
synonymy and a description taken from the average of numerous specimen 
“ Etheostoma pellucidum Baird MSS., ben 
Pleurolepis pellucidus Agassiz in Putnam’s Bulletin Mus. Comp. Zoöl., 1863, 5. 
Cope, Cyprinidæ of Penn., Supplement, 1866, 401. Le Vaillant, Recherches sur les 
Poissons, ete., 1874 Jorden; Indiana Geol. Survey, 1874, 214. Manual Verte- 
brates, 1876, 221. Jordan and Copeland, Check-List, Bull. Buffalo Soc. Nat. Hist., 
1876, 135. Nelson, Bull. Ills. Mus. of Nat. Hist., Dec., 1876, p. 35. Jordan and 
Gilbert, Fishes of Indiana, Indiana Farmer for Jan. 17, 1877. 
