1906.] NATURAL SCIENCES OF PHILADELPHIA. 475 



Cope's statement, that ''the two posterior mandibulars are in con- 

 tact with the median pair of the anterior series, and are separated by 

 a narrow interspace from each other," evidently refers to the teeth 

 of the upper jaw. 



REGANINA gen. nov. 

 Type Myletes bidens Agassiz. 

 Body rather elongate, not entirely orbicular, or not as deep as long. 

 Abdominal profile moderately convex, not pendant. Abdominal 

 •serratures rather numerous, 56. Squamous area on base of anal fin 

 rather low and sharply defined from rest of fin. Adipose fin rather 

 free, not especially enlarged or elongated. No external free short 

 •cultrate predorsal spine. 



(Named for Dr. C. Tate Regan, of the British Museum of Natural 

 History, author of many excellent contributions to Ichthyology.) 

 Heganiua bidens (Agassiz). 



Myletes bidens Cope, Proc. Acad. Nat. Sci. Phila., 1871 (1872), p. 291. 

 Between the mouth of the Rio Negro and the Peru%dan Amazon or Ucay- 



ale River. Robert Perkins. Cope, Proc. Amer. Philos. Soc. Phila., 



XVII, 1877-78 (May 17, 1878), p. 694. Peruvian Amazon. Prof. J. 

 Orton. 



Head 3 ; depth If ; D. v, 14 ; A. iii, 23, i ; abdominal serratures 51 + 5 ; 

 •scales about 85 in lateral line to base of caudal, and 5 more on latter; 

 35 scales between origin of dorsal and lateral line; about 40 scales 

 between vent and lateral line, and same number between root 

 of ventral and lateral line; 46 scales before dorsal; snout 3^ 

 in head, measured from tip of upper jaw; eye 4|; mandible 2|; 

 interorbital space 2^; pectoral 1^; ventral 1^; least depth of caudal 

 peduncle 2f . Gill-rakers 19 + 18, i, lanceolate, and about ^ of longest 

 filaments, which are about equal to orbit. Color in alcohol brownish, 

 belly paler, and fins all more or less brownish, becoming darker margin- 

 ally. Anal with a longitudinal median brown band, anterior radii of 

 fin pale or whitish. Opercle with a brownish blotch. Iris dull yellow- 

 ish. Length 9 inches. Between the mouth of the Rio Negro and the 

 Peruvian Amazon. Robert Perkins, 



This example agrees largely with Agassiz' figure. However, the 

 scales on the base of the anal fin are not indicated as sharply demar- 

 cated from the rest of the same, so that in width this squamous area is 

 but a little broader anteriorly. 

 Mylossoma albiscopus (Cope). 



Myletes albiscopus Cope, Proc. Acad. Nat. Sci. Phila., 1871 (1872), p. 267, 

 PL 12, fig. 1. Cotypes, Nos. 8,014 to 8,021 (type), A. N. S. P. Ambyiacu 



River. John Hauxwell. Cope, I.e., p. 292. Between the mouth of 



the Rio Negro and the Peruvian Amazon. Robert Perkins. 



Width of head 2 in its length ; interorbital space 2^ in head, measured 



