85. PERCID.E AMMOCRYPTA. 489 



slender. Mouth rather wide, terminal, horizontal, the lower jaw in- 

 cluded ; premaxillaries very protractile ; teeth on the vonier. 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 scaly 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. Vertebra} 22 

 + 22 (A. pellticida). Darters of moderate or rather large size, inhabi- 

 ting the sandy bottoms of clear streams, where they bury themselves 

 entirely excepting tbe eyes and snout. Coloration translucent, with 

 bright reflections. (///./.:, sand ; xpuos, concealed.) 

 a. Cheeks and opercles naked; body imperfectly scaled. 



761. A. toeaaai Jordan. 



Body greatly elongated, sub-cylindrical, transparent. Head rather 

 large, heavier than in A. peUucida. Mouth rather wide, 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 apart, about equal in height to 

 the anal fin and 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 black spot on the membrane anteriorly, 

 another near the middle, and some small ones behind; other fins with 

 their membranes dusted with dark points. Head 3^ ; depth 7}. D. X- 

 10 ; A. 1, 9 ; Lat. 1. 65. L. 2 inches. Louisiana and Mississippi. 



(Ammocryvta beanii Jordan, Bull. U. S.Nat. Mus. x, 5, 1877 : Ammocrypta f/clida Hay, 

 Proc. U. S. Nat. Mus. IbSO, 490 apparently the young; the size smaller and the tins 

 lower.) 



aa. Cheeks and opercles scaly. 



762. A. peBlMcMa (Baird) J. & G.Fand Darter. 



Translucent; scales with fine black dots; a series of small, squarish 

 olive or bluish blotches along the back and another along each side; 

 lateral spots connected by a gilt band. Body slender; head stout. 

 Cheeks, opercles, and temporal region scaled ; the scales imbedded and 

 more or less cycloid. Neck above thinly scaled or naked ; scales of body 

 not very rough, those along lateral line and caudal peduncle most 

 closely imbricated; belly entirely naked ; opercle ending in a short, flat 



