ETHEOSTOMATIDZ. 9 
The principal characters separating Hricosma from Alvordius are 
shown below. 
ALVORDIUS, Grd. 
(Type, A. maculatus Grd.) 
_Vertebree numerous, about 44 in 
all; 22 in front of anus. 
Body and head elongate; mouth 
wide, with well-developed teeth on 
vomer and on palatines. 
Sexes similar; males never with 
the fins tuberculate. 
Dorsal spines 12 to 15; the two 
dorsal fins well apart. 
Caudal fin slightly emarginate. 
ERIcosMA, Jordan. 
(Type, Alvordius evides Jor. & Copel.) 
Vertebra fewer, about 39 in all; 
17 in front of anus. 
Body short and compact; mouth 
small, with about six minute teeth 
on vomer and none on palatines. 
Sexes dissimilar; the males bril- 
liantly colored, with the lower fins 
tuberculate. 
Dorsal spines 10 or 11; the two 
fins contiguous. 
’ Caudal fin deeply emarginate. 
6. RHEOCRYPTA, Jordan, gen. nov. 
Allied to Imostoma and Alwordius. Body rather slender and elongate, 
with a pretty large, rather long, and somewhat narrowed head, resembling 
that of Boleosoma; mouth small, horizontal, subinferior, with weak 
teeth in the jaws, five or six small teeth on the vomer, and none on the 
palatines; upper jaw protractile, separated by a distinct furrow from 
the forehead; two distinct dorsal fins, of which the second is rather 
smaller than the first and than anal; anal with two distinct spines; 
ventral region with a series of enlarged plates, as in -lvordius and Per- 
cina, these caducous, in many specimens replaced by a scaleless strip ; 
cheeks naked ; opercles with a few scales; lateral line complete. 
This genus is perhaps nearest Jmostoma, with which it agrees in the 
protractile mouth. 
Grd. in the presence of ventral plates. 
It differs from Jmostoma and agrees with Alvordius 
The name Fheocrypta (peo, to 
flow rapidly—zpouztos, concealed, i. e., hiding in the rapids) is ‘given in 
allusion to the peculiar habits of this interesting species. 
7. RHEOCRYPTA COPELANDI, Jordan, sp. nov. 
Head 44 in length; depth 54; eye large, 34 in head; scales moderate, 
strongly ctenoid, 56 in lateral line; those of the ventral much enlarged, 
forming serrated plates ; cheeks naked ; opercles with a few scales ; neck 
and throat naked. Fin-rays:—Dorsal X-XII, 10; anal II, 9. 
