258 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Veutrals short, not nearly reaching- front of anal, 2 in bead. Pectorals 

 nearly as long as Lead, reaching to beyond base of ventrals. 



Head 4 in length ; depth 3 to 4 ; D. 7 ; A. 8 or 9. Scales 30 or 31-10. 



Color, light olive with some bluish reflections ; each scale edged with 

 dark; a very narrow dark line along median row of scales on sides; toj) 

 of head and upper part of opercle, dusky ; an oblique, narrow and ratlier 

 obscure, dark blue-black band below eye ; a black spot on each side of 

 belly, a dark median line on caudal peduncle below. Fins dusky. 



Exceedingly abundant in the marshes about Lake Poutchartrain. A 

 few specimens were also obtained at Galveston. This species is most 

 closely allied to Gambusia holbroolci (Agassiz) ; a comparison with spec- 

 imens of the latter from Indian Eiver, Florida, show certain constant 

 differences. Thus, in holhrooM the eye is larger, more than one third 

 length of head, and is contained li in interorbital width ; and the head 

 is larger, 3§ in body. These slight differences may disappear on the 

 examination of an extended series, but with our present material no 

 variation is apparent. In the synonomy of holbroolci must be i)laced 

 HaplocMIus melanops Cope. Proc. Amer. Philos. Soc. 1870, 457 {nee 

 Zygonectes melano'ps Jordan. Bull. 111. Lab. Isat. Hist. No. 2, 52) ; and 

 Zygonectes atrilatuH Jordan «& Brayton, Bull. U. S. JSTat. Mus. xii, 1878, 84. 



27. MollienesialatipiniiaLe Sueur. P. (30823,30870.) 



PcccUia muliiUneafa Le Sueur, Jonrn. Acad. Nat. Sci. Philad. 1823, ii, 4. 

 1 Liviia matamorensis Grd. Proc. Acad. Nat. Sci. Phila. 1859, IIG. 



Body oblong, much compressed in males, of nearly equal height from 

 dorsal backwards, the greatest height of body but one-third greater than 

 that of caudal peduncle ; females, with gibbous belly and narrower 

 caudal peduncle ; head very small, depressed, not narrowed forwards ; 

 mouth very small, vertical, and without lateral cleft; lengtli of mandi- 

 ble about two-thir(^?. diameter of orbit ; teeth nil very small, movable, in 

 a rather narrow band ; the outer series much larger than the others, but 

 still very small, composed of slender pointed teeth, strongly curved 

 inwards ; eye moderate, 1^ to 1| in interorbital width, equal to or slightly' 

 greater than snout, and 3J to 3A in head. 



Dorsal very long, in adult males enormously elevated, exceeding- 

 height of body ; the fin is almost square, the base slightly longer than 

 the height, the upper margin nearly straight ; longest ray 2^^ in length 

 of body, the last ray reaching beyond base of caudal; base of fin 2^ in 

 body ; origin of dorsal distant from base of caudal, 24 times its distance 

 from the tip of snout. In females, the dorsal is low, the longest ray 

 equaling two-thirds length of head, the last ray reaching- but half way 

 to base of caudal ; the base of the fin 3f tiuies in length of body, its 

 origin distant from base of caudal IJ times the distance from tip of snout. 



Anal very small ; in the male, modified into an intromittent organ, 

 and inserted in advance of middle of dorsal, its origin about half way 

 between snout and base of caudal, the fourth ray longest and thickest, 1:^ 



