NATURAL SCIENCES OP PHILADELPHIA. 263 



lius wliite. A black scapular spot, and a crimson spot at the apex 

 of each operculum. Opercular bones with purple reflections. 

 The Ambyiacu. 



This genus was proposed by Giinther, in 1869 (Proc. Zool. Soc, 

 p. 424), on the type species, M. cephalus. This fish is evidently 

 nearly allied to the species here described, but is different from 

 them in the larger size of the external series of premaxillary 

 teeth, since they are, according to Giinther, double the size of 

 the maxillaries, nearly in contact, and apparently more denticu- 

 late. It is about as stout as the present fish, but the arrange- 

 ment of the posterior series of teeth is similar to the 31. erythrojj- 

 terus. I have two specimens of the 31. melanopferus, and they 

 agree in every detail. 



MEGALOBRYCON ERYTHROPTERUM, Cope, sp. nov. 



More elongate; length of head equal depth, and one-fourth the 

 length without caudal. Orbit large, 3.5 times in head, 1.8 times 

 in interorbital width. Radii D. 11; A. 23; V. 8, commencing op- 

 posite a point equal to five radii in front of the dorsal fin. Pec- 

 torals 12, not reaching ventrals. Squamation injured, lateral line 

 estimated tO. Teeth similar to the last, except tliat there are 

 twelve premaxillaries on each side, and that those of the posterior 

 row at each end, instead of being continuous with the larger me- 

 dian teeth of that row, are continuous with the lateral limbs of 

 the median M -shaped row, as in 31. cephalus. 



Total length If inches, = .19 m., to dorsal fin .086 m., to anal 

 .115. Color pale and uniform, with a black scapular and large 

 basal caudal spot, which is prolonged as a band to the margin of 

 the fin. Rest of caudal and all the other fins, except base of dorsal, 

 crimson. Sides of head with pearly purple reflections. 



Though the characters separating these species are few, they 

 are important. They are found in the form of body, position of 

 dorsal fin, anal radii, color, and dentition. 



From the Ambyiacu. 



TRIPORTHEUS, Cope, gen. nov. 



Dorsal short, anal elongate. Teeth in three series on the pre- 

 maxillary bone, denticulate, in two rows on the mandible, the 

 posterior of the latter consisting of two convex median teeth. 

 Pectoral region compressed and keel-shaped on account of the 

 1872,J 



