24 PROCEEDINGS OF THE NATIONAL MUSEUM vol, 119 



dentary 1 to 4 in the alizarin specimens. Gill rakers 7+14 (alizarin 

 specimens) . 



Dorsal fin ii,8; anal fin iii,8; pectoral i,8 to i,10; pelvics ii,7. Adi- 

 pose fin present on all specimens, its base above scale row that runs 

 diagonally to posterior base of anal fin. Caudal fin with principal 

 rays 10/9. Distal tips of aU elements of first 10 rays contained in upper 

 caudal lobe. Lower lobe containing all distal tips of remaining 9 

 principal rays. 



Highly modified anal fin of male Nannostomus digrammus (fig. 6) 

 with an interestuig structm-e. Unbranched anterior rays 3, followed 

 by 7 once dichotomus branched rays; terminal or last ray unbranched. 

 Last ray not divided to its base and with its own separate pterygio- 

 phore, or radial series. Except for anteriormost small ray hidden be- 

 low scale at anterior base of anal fin, each of first 6 rays greatly ex- 

 panded anteriorly and posteriorly. These rays arranged as follows in 

 collapsed fin: Second ray (first large ray of anal fin) partially enclosed 

 by anterior edges of ray halves of third anal ray. Thus appressed 

 posterior borders of ray halves of second ray enclosed by 2 diverging 

 anterior borders of thud anal fin ray. Anterior edge of foiuth anal ray 

 (including both ray halves) lymg to left of posterior border of third 

 anal ray. Anterior border of fifth anal ray lying to right of posterior 

 border of third anal ray and to right of entire middle region of fourth 

 anal ray. Sixth anal ray lying to left of posterior border of fifth ray 

 and will even slip to left of posterior border of foiuth ray. Anterior 

 edge of seventh anal ray lying to right of posterior half of sixth anal 

 ray and posterior border of seventh ray lying to right of anterior 

 border of eighth ray. Anterior border of ninth ray lying to right of 

 posterior border of eighth ray, but tenth and eleventh rays with usual 

 position in being just posterior to rays anterior to them. Fourth ray 

 with its left lateral face convex, its right lateral face concave. Fifth 

 ray, converse of fourth, and sixth ray with convex and concave faces 

 facing same sides as fourth ray. This alternation continuing to eighth 

 ray. Ninth through eleventh anal rays with little if any convexity or 

 concavity. 



Inclinator muscles extending bilaterally ventrally far beyond base of 

 anal fin rays and inserting on lepidotrichs to about one-half length of 

 tenth and eleventh anal fin rays. Similarly inclinator muscle extend- 

 ing ventrally beyond scales and inserting along basal one-fifth of 

 second anal fin ray (fig. 6). 



Many male nannostominans and some male pyrrhulininans have 

 anal fins that are modified m a manner similar to that noted here for 

 Nannostomus digrammus. However, none have their anal fin rays 

 modified as greatly as those of digrammus. Species of nannostominans 

 and pyrrhidininans that I have seen breeding in aquaria all have been 



