eigenmann: the cheirodontin^b. 79 



6843a-x, C. M., thirty-five, largest 38 mm. Jaquara, Rio Grande, into Rio 

 Parana. Aug. 18 and 19, 1908. Haseman. 



6845a-e, C. M., five, largest 41 mm. Cacequy, secondary tributary of the Rio 

 Uruguay. Jan. 31, 1909. Haseman. 



Head 3.6-4.5; depth 2.25-3; D. 11; A. 19-27 most frequently 22 or 23; scales 

 31-36, most frequently 33 or 34, 9-12 with spines; eye equal to interorbital, 

 about 2.5 in the head; depth of caudal peduncle 1.25 in its length; base of anal 

 much longer than caudal peduncle. 



Compressed, depth very variable, the dorsal and ventral profiles symmetric, 

 nearly equally arched; preventral area flat, with well-marked lateral edges, eleven 

 to thirteen scales in a median series; predorsal area keeled, with ten scales in a 

 median series, which is regular to near the occipital process; occipital process short, 

 extending one-sixth to one-seventh to the dorsal, bordered by two or three scales; 



Fig. 27. Cheirodon piaba Liitken. a, premaxillary; b, maxillary. 



frontal fontanel an equilateral triangle, 2.5-3.5 in the length of the parietal fon- 

 tanel; interorbital convex; third suborbital covering the entire cheek, or a very 

 narrow naked wedge behind it; lower one of the postorbitals as wide as the third 

 suborbital at its tip, sometimes covering the entire width to the preopercle; the 

 upper postorbital much narrower, leaving a wider naked strip; mouth minute, 

 maxillary not, or barely, reaching the eye, nearly vertical, very little more than 

 half the length of the eye; maxillary with one tooth in three specimens, two teeth 

 in sixty-two specimens, and three teeth in seven specimens examined; premaxillary 

 with five teeth; mandible with about seven teeth; teeth sometimes black-tipped. 

 Gill-rakers about 6 + 11, not over one-fourth as long as eye. 



Origin of dorsal equidistant from tip of snout and base of caudal, the highest 

 ray a little over length of head; origin of anal a little behind vertical from base of 

 last dorsal ray; pectorals reaching to, or beyond, origin of ventrals, ventrals not 

 to anal ; eight to thirteen rays of the anal (beginning with the second or third) of the 

 male with hooks, base of the hook-bearing portion of the anal, making an angle with 

 the base of the rest of the fin; all but the outer two ventral rays with similar hooks; 



