34 



PROCEEDINGS OF THE NATIONAL MUSEUM 



and 5 Avith 32 vertebrae. Precaudal vertebrae 17 to 19 and caudal 

 vertebrae 13 to 14, never in a combination over 33 or under 31 total 

 vertebrae. 



Color in alcohol. — (Specimens from British Guiana). Dorsum 

 of head light to dark brown. Primarily horizontal stripe beginning 

 on lower part of snout tip and tip of lower jaw, extending to pupil of 

 eye, then passing over posterior part of kis, across foiu:th and fifth 

 orbitals to posterior edge of operculum. Primary horizontal stripe 

 then continuing from under fleshy opercvdar flap posteriorly over lower 

 portion of third scale row and upper half of fourth scale row to termi- 

 nate as narrow black wedge on caudal fin. On caudal peduncle, 

 primary horizontal stripe expanding downward to cover aU but 

 lowermost ventral scale row. 



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Figure 8. — Nannostomus marginatus, male, SL 19.5 mm., CAS(IUM) 11700 (see text for 

 discussion of teeth). 



Pale silvery stripe extending from eye onto caudal fin above primary 

 horizontal stripe. Melanophores scattered over entire surface of this 

 silvery stripe, thickest and heaviest in region of third through about 

 eighth and thirteenth or fourteenth to sixteenth vertical scale rows. 

 These darker areas representing oblique bands, one anterior, one pos- 

 terior to dorsal fin. Silvery band most pale over hypural fan and on 

 caudal fin between wedge-shaped portions of primary and secondary 

 horizontal stripes. Secondary horizontal stripe dorsal to pale lateral 

 stripe. Secondary stripe extending above opercular bone through 

 upper part of second lateral scale row onto caudal fin, terminating on 

 this fin as an acute wedge. Dorsum dark above secondary horizontal 

 stripe, rather densely covered with melanophores, especiaUy behind 

 dorsal fin. Below primary horizontal stripe, sides white to very pale 



