10 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ii9 



Head elongate, snout obtuse in vertical and horizontal profiles. 

 Top of head very slightly convex between eyes. Head 3.6 (3.5 to 3.7) ; 

 eye in head 3.0 (2.9 to 3.0); snout in eye about 1.0 in all specimens 

 examined; least width of bony interorbital in greatest eye diameter 

 1.0 or very slightly less in all specimens examined, 



Premaxillary with 7 teeth. Each tooth except posterior 1 or 2 

 with 5 cusps. Posterior 2 teeth usually quadricuspid. Sometimes 

 most anteromedial premaxillary tooth with only 4 cusps. Usually with 

 largest cusp just medial to farthest posterolateral cusp. Maxillary 

 with single, uni- to quadricuspid tooth. Teeth in anterior row of 

 each dentary 7 to 8. Anterior 5 or 6 teeth hexacuspid, third from 

 anteromedial cusp largest. Posteriormost dentary tooth usually tri- 

 cuspid. Second dentary tooth row with 8 to 11 unicuspid teeth. Gill 

 rakers 10-f 17 on each first gill arch in one alizarin preparation, 

 SU 50252. 



Dorsal fin rays ii,8; anal iii,9; pectoral i,10; pelvics ii,7, in all 

 specimens examined. Adipose fin present, well developed in all 

 specimens. Caudal fin with principal rays 10/9; distal tips of all 

 ray elements of first (upper) 10 principal rays within upper caudal 

 lobe; remaining 9 principal rays end in lower lobe. 



Male's anal fin modified (fig. 1) ; rays somewhat expanded and 

 more similar to highly modified anal rays of Nannostomus digrammus 

 than any other species of Nannostomma. 



Radial grooves of scales in third horizontal scale series below 

 dorsal fin shown in figure 1. Posterior field of each scale with 2 to 3 

 radial grooves; dorsal and ventral fields each with 1 radial groove; 

 anterior field with 2 to 4 radial grooves. Dorsal and ventral anterior 

 corners of scales in this species more acute than in any other species 

 of Nannostomina. Acute corners very similar to those found in sub- 

 tribe Pyrrhulinina. Scales in lateral series 22 in all specimens ex- 

 amined. Perforated lateral-line scales on each side 1 or 2. Scales in 

 median predorsal series 10 in all specimens examined. Total number 

 of vertebrae 33 (18 precaudals and 15 caudals) in all specimens. 



Color in alcohol. — Preserved specimens (SU 50214) have the 

 following color: Top of head hght to dark bro\\Ti. Primary horizontal 

 stripe from tip of snout across maxillary and first obrital bones onto 

 anterior part of iris of eye; then from posterior part of iris to edge of 

 opercular bone. Posterior to eye, primary horizontal stripe somewhat 

 diffuse and hard to distinguish. Primary horizontal stripe behind 

 operculum represented as very diffuse, slightly darkened area ex- 

 tending posteriorly to caudal peduncle, through third and foiu-th 

 longitudinal scale rows. (In live specimens kept in an aquarium wdth 

 dark brown peatmoss bottom and subdued light, horizontal stripe 

 became much darker but remained diffuse.) Large permanent blotches 



