216 PROCEEDINGS OF THE NATIONAL MUSEUM vol.94 



16. Total length of adipose fin contained about iVz to 5 times in standard length; 



first dorsal ray longer than lengt h of adipose fin ; caudal fin base with a pair 



of hidden or embedded dark spots, persistent at all sizes. 



2a. Lower lobe of caudal fin with a darkish oblong blotch, below which ventral 



margin of caudal fin is distinctly pale or whitish; upper sides and back 



a])0ve the lateral line grayish or brownish, below which the sides are pale, 



distinctly set oQ' from darker pigment above, pale sides extending about 



an eye diameter above black lateral line; distance from base of dorsal to 



origin of adipose fin a little greater than snout and eye; anal rays v, 8 



to 10, usually 9 branched rays; pectoral rays I, 13 or I, 14; gill rakers 2 



or 3+10 or 11. 



Megalonema platycephalum psammium, new subspecies 

 26. Pigment of lower lobe of caudal fin not restricted to a large blotch set oflf 

 ventrally by a white ventral margin on lower caudal lobe; pigment on 

 back and sides extends below lateral line anteriorly and along it posteri- 

 orly, no pale area above lateral fine; distance from base of dorsal to origin 

 of adipose equal to snout and eye. 



Megalonema platycephalum platycephalum * Eigenmann 



MEGALONEMA PLATYCEPHALUM PSAMMIUM, new subspecies 



Plate 2, B 



Holotype.— U .S.N M. No. 121175, a specimen 133.5 mm. in standard 

 length, taken by Leonard P. Schultz in the Rio Pahnar at the bridge, 

 70 km. southwest of Maracaibo, March 6, 1942. 



Paratypes (all collected by L. P. Schultz).— U.S.N. M. No. 121178, 

 15 specimens, 74 to 105 mm., taken along with the holotype and 

 bearing the same data; U.S.N.M. No. 121177, 46 examples, 35 to 152 

 mm., Rio Socuy, 3 km. above mouth, February 24, 1942; U.S.N.M. 

 No. 121176, 14 specimens, 64.5 to 102 mm., Rio Apon, about 35 km, 

 south of Rosario, Maracaibo Basin, February 26, 1942. The specimens 

 were taken mostly over sandy bottoms. 



Description. — The holotype and one paratype were carefully meas- 

 ured, and data for these, expressed in hundredths of the standard 

 length, are recorded below, respectively. Standard length (in mm.) 

 133.5 and 107. 



Length of head to end of supraoccipital 28.5 (29.4) ; length of head 

 to end of gill cover 28.8 (29.0) ; greatest depth of body at dorsal origm 

 15.0 (16.1); width of head at base of pectorals 16.2 (16.3); length of 

 snout 12.7 (13.1); diameter of eye 4.42 (4.86); width of fleshy inter- 

 orbital space 7.34 (6.73) ; width of bony interorbital space 5.02 (4.67) ; 

 distance from margin of eye to posterior nostril 5.77 (5.89) ; distance 

 from anterior to posterior nostril 4.64 (4.65); postorbital length of 

 head 12.1 (11.7); total length of adipose fin 22.8 (21.1); height of 

 adipose 5.62 (6.54) ; least depth of caudal peduncle 8.32 (7.85) ; length 

 of caudal peduncle or distance from rear of anal base to midbase of 

 caudal fin 18.0 (18.2); length of first ray of dorsal 23.2 (24.8); length 



4 This species is known from Tumatumari, British Guiana, in the original description by Eigenmann, 

 Mem. Carnegie Mus., vol. 5, p. 150, fig. 31. pi. 10, fig. 2, 1912. 



