85. PERCID^ AMMOCRYPTA, 
489 
slender. IMontli rather wide, terminal, horizontal, the lower jaw in- 
cluded ; preinaxillaries very protractile ; teeth on the vomer. Scales 
thin, ctenoid, little imbricated, present along: the region of the lateral 
line and on the tail, sometimes wanting on the back or belly.; lateral line 
complete. Head scalj" or naked ; no ventral plates ; the belly naked. 
Gill-membranes considerably united, forming an angle at their junction. 
Dorsal fins moderate, about equal to the anal fin and to each other ; 
dorsal with about ten spines; anal spine single, weak. Vertebrm 22 
+ 22 (A. pdlucida). Darters of moderate or rather large size, inhabi- 
ting the sandy bottoms of clear streams, where they bury themselves 
entirely" exceiiting the eyes and snout. Coloration translucent, Avith 
bright rellections. sand; y.pu-roq^ concealed.) 
a. Cheeks aud opercles naked; body imperfectly scaled. 
161. A. toeaBJa .Jordan. 
Body greatly elongated, snb-cylindrical, transparent. Head rather 
large, heavier than in A. pellucUJa. Mouth rather tvide, nearly termi- 
nal ; the upper jaw somewhat the longer; outer teeth strong, hooked. 
Opercular spine obsolete. Head entirely naked. Body naked, except 
the caudal peduncle, which is sparsely covered with thin, imbedded 
scales, and a series of rather large scales along the sides, on which the 
lateral line runs. Dorsal fins high, wide a])art, about equal in height to 
the anal fin aud to each other; caudal fin emarginate. Color trans- 
lucent, without bars or spots, the lateral line shining-golden in life. 
Spinous dorsal with a large l)lack spot on the membrane anteriorly, 
another near the middle, and some small ones behind; other fins Avith 
their membranes dusted with dark points. Head ; depth 7^^. D. X- 
10 ; A. 1, 0 ; Lat. 1. 05. L. 2J inches. Louisiana and Mississippi. 
(AmmocriiDta heanii Jordan, Bull. U. S.Nat. Mns. x, 5, 1877 : Ammocrypta gelida Hay, 
Proc. U. S. Nat. Mns. 1880, 400 — apparently the young; the size smaller and the tins 
lower.) 
aa. Cheeks and opercles scaly. 
TOtJ. A. sscBSsacida (Baird) .1. &. G. — Sand Darter. 
Translucent; scales AAuth fine black dots; a series of small, squarish 
olive or bluish blotches along the back ami another along each side; 
lateral sjtots connected by a gilt band. Body slender ; head stout. 
Cheeks, opercles, and temporal region scaled ; the scales imbedded and 
more or less cycloid. Xeck aboA’e thinly scaled or naked ; scales of body 
not A'ery rough, those along lateral line and caudal iteduncle most 
closely imbricated; belly entirely naked; opercle ending in a short, flat 
