420 CALIFORNIA ACADEMY OF SCIENCES. 48 



pectoral i% longer than head, 3^ in body; caudal 

 slightly longer than head ; interorbital space broad, nearly 

 equal to eye. 



Body much compressed, the belly sharp edged, con- 

 cave on each side below pectorals, as if pinched together 

 between the fingers, the ribs reaching the edge, the scales 

 passing around it: the edge almost cavinate. Back 

 narrow. Scales smooth, none on dorsal or anal. Mouth 

 small, terminal, the short jaws curved, the structure pre- 

 cisely as in Menidia, the teeth moderate, curved, those in 

 the upper jaw longer; opercles oblique behind, not ver- 

 tically truncate. Gill-rakers numerous, long and slender. 

 Pectorals very long and falcate, reaching to front of anal 

 and beyond tips of the short ventrals, their posterior mar- 

 gin concave; spinous dorsal small, inserted midway be- 

 tween edge of preopercle and base of caudal, about over 

 sixth ray of anal; last ray of dorsal considerably before 

 last of anal; base of anal \% times length of head, 2% 

 in body. 



Color, light green, much dotted above, translucent be- 

 low; a black streak of dots along base of anal; some on 

 sides of head; median line of back dusky; fins all pale; 

 no black on spinous dorsal, ventral or pectoral; lateral 

 stripe % width of eye, underlaid by black; a large, per- 

 fectly transparent, space above front of anal, marking 

 the posterior portion of the air-bladder. 



Length, 2)4 to 3 inches. Rather common in the estu- 

 ary at Mazatlan. 



About twelve specimens obtained, numbered 2688 in 

 the L. S. Jr. Univ. Mus. 



64. Thyrina crystallina Jordan & Culver, n. sp. 



Rather common in the Rio Presidio in fresh water; not 

 seen elsewhere. It is apparently not found in the sea, 

 but confined to fresh or brackish waters. 



