412 CALIFORNIA ACADEMY OF SCIENCES. 40 
jenkins?, the head is much larger and the form more ro- 
bust, besides slight differences in the scales. The speci- , 
mens obtained were sent to us by Senor Ygnacio Moreno 
after our departure from Mazatlan. 
Family P@!CILIIDAL. 
53. Pecilia butleri Jordan. 
Common in the fresh waters of the Rio Presidio below 
the village of Presidio, where the species was originally 
taken by Mr. Alphonse Forrer. 
Head 3%; depth 234 to 3%; dorsal 9; anal 6; scales 
26-9: eye 3 in head, equal to snout; interorbital 2; pec- 
toral 1% in head; caudal equal to head. Longest dorsal 
ray 1% inhead in male; 1% in female. 
Body much deeper and more compressed than in Pacr- 
lia presidionis, the profile rather steeply rising to front of 
dorsal. Dorsal and ventral outlines of head meeting at 
mouth and forming a somewhat sharp point; snout as 
viewed from above, truncate. Teeth in two series, the 
inner smaller, more close set, not trifid, the two series 
well separated. Interorbital space wide and flat, about 
twice as wide as eye. 
The sexes difter greatly in the position of the anal fin, 
itis under or rather behind dorsal in females, much in 
front in males, the tips of ventrals reaching much past 
the base of fin. The sexes similar in size, not very unlike 
in coloration; both with traces of faint olive cross-bands, 
especially on caudal peduncle; a dark curved streak be- 
,hind eye on opercle bounding a roundish silvery area on 
opercle and breast. 
Male green with pale blue spots on each scale sur- 
rounded by pale bronze shades; no bars. Dorsal and 
caudal pale orange, with many small black spots. Lower 
fins pale. Female similar, paler, without cross-bands, 
