19. TETRAGONOPTERUS. 329 



i 

 total length (without caudal), the length of the head one-fourth ; 

 the width of the interorbital space is more than the diameter of the 

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

 head. Upper profile of the head not concave. The maxillary termi- 

 nates in the vertical from the front margin of the eye. The origin 

 of the dorsal is nearly above that of the ventral. Pectoral not 

 reaching to the ventral. J3asal portion of the caudal fin scaly. 

 Humeral and caudal spots present, united by a silvery band ; the 

 naked portion of the upper caudal lobe black. (Kner.) 

 Rio Guapore. 



28. Tetragonopterus taeniatus. 

 Jenyns, ZooL Beagle, Fish. p. 126 ; ? Cuv. fy Vol. xxii. p. 145. 

 D. 11. A. 25. L. lat. 40. L. transv. 7/6. 



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

 caudal). The ventrals are in an exact bine with the commencement 

 of the dorsal. Humeral and caudal spots present, united by a silvery 

 band. (Jen.) 



Socego (province of Rio de Janeiro). 



b. Cleft of the mouth rather wide ; maxillary without teeth along its 

 edge, long and narrow, extending to, or nearly to, below the centre 

 of the eye. Dorsal fin above the ventral. 



29. Tetragonopterus melanurus. 



Salmo melanurus, Bl. taf. 381. fig. 2. 



Tetragonopterus melanurus, Mull. § Trosch. Hor. Ichth. i. p. 14 ; Cuv. 

 Sf Vol. xxii. p. 155. 



D. 11. A. 26-30. V. 8. L. lat. 45-46. L. transv. 7/4$. 



The height of the body is contained thrice and a half or four times 

 in the total length (without caudal), the length of the head four 

 times and a half or four times and one-third. Interorbital space 

 flat, its width being equal to the diameter of the eye, which is two- 

 fifths of the length of the head. Upper profile straight above the 

 occiput. Maxillary long and narrow, extending to, or nearly to, 

 below the middle of the eye. The origin of the dorsal fin is vertically 

 above that of the ventral ; the pectoral extends to the base of the 

 ventral. Uniform silvery ; caudal fin black, with two large orange- 

 coloured spots on its basal half. 



Guiana. 



a. Adult. British Guiana. Presented by Sir R. Schomburgk. 

 b-c. Adult. Essequibo River. Prom Mr. Ehrhardt's Collection. 

 d. Adult. Prom the Collection of the Zoological Society. 



30. Tetragonopterus aflinis. 

 D. 11. A. 27. V. 8. L. lat. 43. L. transv. 7/4$, 

 Very similar to T. melanurus, but with the head comparatively 



