[39] REVIEW OF THE SCLENIDA. 381 
This genus consists of fresh-water Scizenoids, inhabiting the rivers of 
South America. The genus seems to us a valid one, although closely 
allied to Corvula and Pseudotolithus, from both of which it is well dis- 
tinguished by the peculiar squamation of the lateral line. This char- 
acter suggested to Dr. Steindachner the name JDiplolepis, a name 
which is, unfortunately, preoccupied. As no species of Plagioscion was 
named by the describer of that genus, we have hesitated as to the 
propriety of making use of that name. The original description of 
Plagioscion must, however, certainly have been based on some species 
of the present genus, as it agrees with no other American form. We 
have therefore retained the name given by Dr. Gill in preference to 
coining some new one for the group. 
Like most fresh-water fishés, the species of Plagioscion are subject to 
many variations, especially in regard to the size of the second anal 
spine. But three of the numerous nominal species seem to us valid. 
ANALYSIS OF SPECIES OF PLAGIOSCION. 
a. Second anal spine small, scarcely longer than eye, its length 4 to 54 in head; teeth 
of lower jaw with the inner series considerably enlarged; snout of moderate 
length, 5 in head; eye,54; maxillary, 2}in head; gill-rakers rather long, X+-12; 
pseudobranchiz usually small on one side and obsolete on the other; upper part 
of the preopercle crenulate on its bony margin; pectoral fin short, 13 in head‘ 
anal spine, 4} to 54, its length subject to much variation ; caudal convex; ven- 
trals filamentous at tip. Color, silvery; darker above, the axil with a large 
black spot. Head 3} in length; depth 3}. D. X-I, 31 or 32. A.II,7. Scales 
(large ones or pores) 49 to 53. Lower pharyngeals narrow, armed with villiform 
Cee eee 2 eR ends obs send i 6 45s SQUAMOSISSIMUS ae 
aa. Second anal spine large and strong, its length 2 to 3 in head. 
b. [Teeth of lower jaw with the inner series considerably enlarged ; snout very 
short, blunt, 5}in head; head depressed above the eyes; mouth large, rather ob- 
lique, subinferior, the maxillary 24 in head, reaching past eye; back elevated ; 
ventral outline nearly straight ; caudal peduncle slender ; preorbital broad, a lit- 
tle narrower than eye, which is 5} in head; preopercle rounded, nearly or quite 
entire ; teeth of outer series in upper jaw and inner series of lower notably en- 
larged; dorsal spines slender, the highest 2? in head; pectoral 1} in head; ven- 
trals 12; scales all ctenoid; head 32; depth 32; D. X-I, 31 to 33. A.II,6. En- 
larged scales in lateral line about 50; about 100 in a longitudinal series above it. 
Color grayish above, silvery below; upper vertical fins punctate; lower fins yel- 
lowish’s “axil dark. (Steimdachner:)) 22. 22. 222) 2 2 ecess.- Boe SURINAMENSIS, 38. 
bb. Teeth of lower jaw subequal, those of the inner row scarcely enlarged ; head very 
convex above, not spongy ; preopercle with a broad membranous margin, which is 
slightly crenulate; preorbital broad, as broad as eye ; mouth large, oblique, the 
lower jaw slightly included, the maxillary 27 in head; snout bluntish, 3¢ in head, 
eye 6 in head ; gill-rakers X + 13, slender and moderately long, the longest about 
2 diameter of eye; outer teeth above somewhat enlarged; pectorals long, 13 in 
head, shorter than the ventrals, which have filamentous tips; second anal spine 
24 to 23 in head; dorsals connected, the soft dorsal largely scaly at base ; caudal 
rhombic, the middle rays produced. Color plain silvery, the axil dusky. Head 
34; depth 3}. D. X-I, 34 to 36. A.II,7. Scales 49 (pores); 80 cross-series. 
AURATUS, 39. 
