Occasional Papers of the Museum of Zoology 5 



Gill-rakers slender, shorter than the pupil, 17 on lower limb of 

 outer arch. Air-bladder rather faintly showing through the semi- 

 translucent flesh, extended backward as a well-defined and bluntly 

 pointed diverticulum into the urosome over the anal base. 



Scales in 41 (38 to 41) rows from gill-opening to end of hypural; 

 mostly without, but occasionally with a few widely spaced and 

 rather indistinct apical radii; scale margin either entire or slightly 

 uneven, or coarsely yet weakly laciniate. 



Variation in the Number of Anal Rays in Four Series of 

 Thyrina colombiensis 



Dorsal rays III (or IV), 8 (7 to 9); anal rays, I, 19 (16 to 21: 

 see table). Spinous dorsal located a little behind vertical from 

 front of anal fin, when depressed extending nearly two-thirds (to 

 about one- half) the distance to the origin of the second dorsal; 

 second dorsal with a short base (about equal to postorbital length 

 of head), extended backward about to vertical from end of anal 

 base. Anal base shorter than in other species of Thyrina excepting 

 T. brasiliensis, only about as long as head; anal edge falcate. 

 Origin of anal fin about midway between head and base of caudal, 

 considerably more anterior in relative position in young. Pectoral 

 fin about as long as head (usually slightly longer than head in the 

 Telembi series, slightly shorter than the head in the lots from the 

 San Juan basin); length of pectoral contained 4.2 (3.9 to 4.3) 



