300 PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



the dorsal slightly in advance of the anal, without spines. Scales mod- 

 erate. Limnophagous. Sexual changes, if any, unknown. 



This genus differs from the most of the other Cyprinodontidce in its 

 tricuspid teeth. From Gyprinodon, Jordanella, Fitzroyia, Characodonj 

 and Jenynsia, the genera thus far known with tricuspid incisors, it is 

 distinguished by the elongate intestines, and by the freeness of the 

 dentary bones. The aspect is wholly unlike Gyprinodon, resembling 

 rather Fundulus. 



Specefic description. — Body oblong, considerably compressed, 

 formed much as in Hydrargyra, the back nearly straight, little elevated, 

 caudal ijeduncle deep. Depth of body 4-4J in length. Head short, 

 broad, depressed, triangular and rather j>ointed, when viewed from the 

 side. 



Mouth quite small, anterior oblique, the lower jaw projecting. Both 

 jaws with a series of rather slender tricuspid teeth, which are loosely 

 inserted, and somewhat movable, not close enough set to form a con- 

 tinuous cutting edge. Head 4 in length. Eye moderate, directed 

 partly downwards, 3^ in head, rather longer than snout and little more 

 than half the width of the very broad interorbital space. A slight ridge 

 from the occipital region backward. 



Scales rather large, 37 to 40 in a longitudinal series, and 13 in a 

 transverse series. Humeral scale somewhat enlarged. 



Fins small. Dorsal fin posterior, very slightly in advance of the 

 anal, which is also short and low, the two fins about coterminous and 

 falling far short of the caudal. Caudal short and small. Vehtrals 

 small. 



Pectorals small, not reaching ventrals. Dorsal rays 12, anal rays 13. 



Color bluish above in spirits, sides nearly plain, with a silvery streak 

 along each series of scales. Vertical fins obscurely marked, each of 

 them chiefly black, especially on the distal half. There is no evidence 

 of any modification of the anal fin in any of the specimens, which are, 

 however, apparently adult. One of the two larger ones is apparently a 

 female, the other probably a male. 



The intestinal canal is considerably convoluted and filled with mud. 



The types of this species, I^o. 23137, are numerous specimens of vari- 

 ous sizes ; the two largest nearly 4 inches in length, were obtained by 

 Professor Duges at L6on in Guanajuato. 



Zophendum australe Jordan, sp. nov. 



Allied to Zophendum siderium (Cope), but with larger scales. 



Body rather elongate, formed much as in Gampostoma anomalum, 

 somewhat compressed, the back somewhat elevated and rounded ante- 

 riorly. Depth, 4^ in length to base of caudal. 



Head rather large, shghtly depressed or flatfish above, its length 

 about 4 times (in length) to base of caudal. Mouth moderate, low, the 

 lower jaw shghtly included, the premaxillary below the level of the eye, 

 the maxillary just reaching the front of the eye. Lower jaw thin-edged, 



