320 chaeacixid^:. 



6. Tetragonopterus polylepis. 



D. 11. A. 34. V. 8. L. lat. 43. L. transv. ^. 



Body much compressed and elevated, its greatest depth being con- 

 tained once and four-fifths in the total length (without caudal) ; the 

 lower profile much arched. The length of the head is one-fourth 

 of the total (without caudal); interorbital space very convex, its 

 width being much more than the diameter of the eye, which is one- 

 third of the length of the head. The upper profile is concave above 

 the parietal region. The maxillary terminates in the vertical from 

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

 behind the root of the ventral. The pectoral extends a trifle beyond 

 the base of the ventral. Uniform silvery. 



British Guiana. 

 a. Four and a half inches long. Presented by Sir K. Schomburgk. 



7. Tetragonopterus chalceus. 



Tetragonoptrus argenteus etc., Artedi, in Seba, iii. tab. 34. fig. 3. 



Coregonus amboinensis, Artedi, Species, p. 44. 



Tetragonopterus chalceus, Agass. in Spix, Pise, Bras. p. 70. tab. 33. 



fig. 1 j Cuv. $ Val. xxii. p. 140. 

 schomburgkii, Cuv. fy Val. xxii. p. 137. 



D. 12. A. 33-34. L. lat. 30-32. L. transv. 7/4|. 



The height of the body is contained twice in the total length (with- 

 out caudal), the length of the head thrice and three-fourths ; inter- 

 orbital space flat, its width being rather less than the diameter of the 

 eye, which is contained twice and one-third in the length of the 

 head. The upper profile is concave above the parietal region. The 

 maxillary extends a little beyond the front margin of the eye. The 

 vertical from the origin of the dorsal fin falls immediately behind the 

 root of the ventrals. The pectoral reaches a little beyond the base 

 of the ventrals. A dark spot behind the shoulder is scarcely visible, 

 and sometimes disappears entirely ; base of the caudal more or less 

 distinctly blackish. 



British Guiana, Brazil. 

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

 c. Fine specimen. Essequibo. From Mr. Ehrhardt's Collection. 



8. Tetragonopterus orbicularis. 



Cuv. Sf Val. xxii. p. 138 ; Casteln. Anim. Amer. Sud, Poiss. p. 65. pi. 32. 

 fig. 3 ; Kner, Denkschr. Acad. Wiss. Wien, 1859, xvii. p. 174. 



D. 11. A. 34. L. lat. 35. 



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

 caudal), the length of the head one-fourth. The upper profile of 

 the head is concave ; the diameter of the eye is two-fifths of the 

 length of the head. The pectoral extends beyond the root of the 

 ventral. Humeral and caudal spots generally present, and united by 

 a silvery longitudinal band. {Val.) 



Amazons ; ? Essequibo. 



