85. PERCID.E — AMMOCRYPTA. 489 



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

 cluded; premaxillarios 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 hack or belly ; lateral line 

 complete. Head scaly or naked; no ventral plates; the belly naked. 

 Gill-mendiranes considerably united, forming an angle at their junction. 

 Dorsal tins moderate, about equal to the anal fin and to each other; 

 dorsal with about ten spines; anal spine single, weak. Vertebrai 22 

 + 22 {A. pellucida). Darters of moderate or rather large size, inhabi- 

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

 entirely excei)ting the eyes and snout. Coloration translucent, with 

 bright reflections. {a,'j.,'>.o^, sand] z/>6»-ro?, concealed.) 

 a. Cheeks and opereles naked; body imperfectlj' scaled. 

 TGI. A. fcctatai .Jordan. 



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

 large, heavier than in A. iidhicida. Mouth rather wide, nearly termi- 

 nal ; the upper jaw somewhat the longer ; outer teeth strong, hooked. 

 Opercular spine obsolete. Head entirely naked. Body nuked, 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 

 latei-al line runs. Dorsal fins high, m ide 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. 

 Si)inous 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 i)oints. Head 33 ; depth Ih. D. X- 

 10 ; A. T, 9 ; Lat. 1. 05. L. 2i inches. Louisiana and Mississippi. 



{Ammo(:)-if)>t(i Iwcitiii .lordati, Hull. U. S.Nat. Mus. x, .5, 1877 : Ammocrjipta ijclida Tlay, 

 Proc. U. S. Nat. Mus. IcHU, 490 — apparently the young; the size smaller and the lius 

 lower.) 



aa. Cheeks and opereles scaly. 



762. A. pelJtacada (Baird) .T. & G.— Sand Darter. 



Translucent; scales with fine black dots; a series of smnll, 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, opereles, and temj)oral 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, ilat 



