19. TETRAGONOPTERUS. 327 



culum. The upper profile of the head is nearly straight. The max- 

 illary extends to below the end of the first infraorbital bone, and 

 terminates a little behind the front margin of the eye. Second infra- 

 orbital with radiating striae. The origin of the dorsal fin is vertically 

 behind the root of the ventrals. The pectoral does not extend to the 

 ventral. An ovate black spot on the shoulder, above the lateral line ; 

 another black spot on the root of the caudal, both spots being united 

 by a black band. 

 British Guiana. 

 a. Adult. Presented by Sir E. Schomburgk. 



22. Tetragonopterus peruvianus. 



Tetragonopterus peruanus, Mull, fy Trosch. Hor. Ichth. i. p. 28. taf. 8. 

 fig. 1 ; Cuv. $ Val xxii. p. 153. 



D. 11. A. 30. L. lat. 36. L. transv. 6/6. 



The height of the body is one-third of the total length (without 

 caudal), the length of the head two-sevenths. The width of the 

 interorbital space is more than the diameter of the eye, which is one- 

 fourth of the length of the head, and much more than the distance 

 between orbital edge and posterior margin of the prseoperculum. The 

 upper profile of the head is not concave. The maxillary extends to 

 below the end of the first infraorbital bone, and to behind the front 

 margin of the eye. The origin of the dorsal fin is vertically behind 

 the root of the ventrals. The pectoral reaches to the ventral. A 

 blackish longitudinal band above the lateral line, becoming darker 

 posteriorly on the caudal fin. (M. <$f T.) 



Peru. 



23. Tetragonopterus humilis. 

 D. 11. A. 27-31. V. 8. L. lat. 36. L. transv. 7/7. 



The height of the body is less than one-third of the total length 

 (without caudal), the length of the head less than one-fourth. Inter- 

 orbital space convex, its width being much more than the diameter 

 of the eye, which is contained thrice and two-thirds in the length of 

 the head. The upper profile of the head is straight. The maxillary 

 terminates in the vertical from the front edge of the orbit. The 

 origin of the dorsal is vertically behind the root of the ventrals. The 

 pectoral reaches to, or a little beyond, the base of the ventrals. Hume- 

 ral and caudal spots more or less distinct ; sides silvery ; anal and 

 ventral with broad red margins. 



Guatemala. 

 a-d. Adult (4| inches long) and half-grown. Lake of Amatitlan. 

 From Mr. Salvin's Collection. 



24. Tetragonopterus oligolepis. 



D. 11. A. 24. L. lat. 28. L. transv. 5/3|. 



The height of the body is two-fifths of the total length (without 

 caudal), the length of the head one-fourth. Interorbital space con- 



