Occasional Papers of the Museum of Zoology 3 



entire or weakly laciniate; rami of mandibles little elevated posteriorly: 

 Colombia to Brazil. 



cK Scales mostly marked with numerous though faint radial af>ical 

 radii; scale margins usually weakly but finely laciniate; air-bladder 

 not showing through the opaque flesh, scarcely extended backward 

 into urosome; dorsal rays II or III, 6 or 7; spinous dorsal when 

 depressed usually reaching less than halfway to origin of second 

 dorsal: salt and brackish loatcrs from Lake Maracaibo, Venezuela, to 

 Rio dc Janeiro, Brazil. 



Thyrina brasiliensis (Quoy and Gaimard). 



c^ Scales mostly without, occasionally with a few widely spaced faint 

 apical radii; scale margins either entire or slightly uneven, or weakly 

 and coarsely laciniate; air-bladder showing rather faintly through 

 the semitranslucent flesh, extended backward as a well-defined 

 conical diverticulum in the urosome; dorsal rays III or IV, 7 to 9; 

 spinous dorsal when depressed usually reaching more than halfway 

 to origin of second dorsal: San Juan and Patia rivers, Colombia. 



Thyrina colombiensis Hubbs. 



Belly shortened, the origin of the anal fin much nearer head than caudal 

 base; anal base decidedly longer than head; air-bladder showing through 

 the translucent flesh, extended backward as a broad diverticulum in the 

 urosome; anal rays 18 to 25: lakes, rivers, and estuaries of Middle America. 



d\ Mouth strongly oblique; rami of mandibles strongly elevated 

 posteriorly; body only moderately elongate: Great Lakes of 

 Nicaragua Thyrina sardina (Meek), 



d^. Mouth little oblique anteriorly, but strongly curved downward 

 posteriorly; rami of mandibles slender, little elevated within the 

 mouth. 



e'. Snout decidedly longer than eye: basin of the Motagna, 

 Atlantic slope of Guatemala Thyrina meeki Miller. 



e^. Snout about equal in length to eye. 



f'. Depth of body less than one-sixth the standard length: 

 Atlantic coast streams of Costa Rica and Panama. 



Thyrina chagresi (Meek and Hildebrand). 



f^. Depth of body more than one-sixth the standard length: 

 Pacific coast slope of Mexico and Guatemala. 



Thyrina guatemalensis (Giinther), balsana (Meek), 

 crystallina Jordan and Culver, and evermanni 



Jordan and Culver.' 



' These species have lately been compared by Jordan and Hubbs, op. cit., 

 pp. 60, 61. 



