19. TETRAG0N0PTERT7S. 319 



b. The entire edge of the maxillary is denticulated. 



4. Tetragonopterus artedii. 

 Cuv. Sf Val. xxii. p. 128 (not synon.). 



D. 11. A. 40. V. 8. L. lat. 30. 



The height of the body is not less than one-half of the total length 

 (without caudal), the length of the head about one-fourth. Upper 

 profile of the head concave ; diameter of the eye rather more than 

 the width of the interorbital space, and one-half of the length of the 

 head. The pectoral extends beyond the root of the ventrals. Max- 

 illary with a few conical teeth near its articulation, its entire edge 

 being finely denticulated. Body with silvery longitudinal bands, 

 without dark cross-bands. (Val.) 



According to Valenciennes, this species would be conspicuously 

 distinguished from T. argenteus and T. rujtpes by the peculiar denti- 

 culation of the maxillary bones. But it is quite evident that it is not 

 the species examined by Artedi and figured by Seba, which agrees 

 in every respect with T. chalceus. 



B. Anal rays less than forty. 



a. Cleft of the mouth of moderate width ; maxillary without teeth along 

 its edge, extending to, or not much beyond, the front margin of 

 the eye. 



a. The height of the body is one-half, or more than one-half, of 

 the total length (without caudal). 



5. Tetragonopterus compressus. 

 D. 11. A. 33. V. 9. L. lat. 35. L. transv. 9/9. 



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

 tained once and two -thirds in the total length (without caudal). 

 The lower profile is subsemicircular, and the pectoral fins are inserted 

 at some distance above the ventral profile. The length of the head 

 is one-fourth of the total (without caudal) ; interorbital space con- 

 vex, its width equalling the diameter of the eye, which is two-^fths 

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

 the parietal region. The maxillary does not extend beyond the ver- 

 tical from the front margin of the eye. The origin of the dorsal fin 

 is vertically a little in front of that of the ventral. The pectoral 

 reaches beyond the root of the ventrals. Silvery, with golden re- 

 flexions ; back bluish ; a round bluish spot on the shoulder, above 

 the lateral line. 



Guianas, Brazil. 



a-b. Fine specimens, 3 inches long. Essequibo. From Mr. Ehr- 



hardt's Collection. 

 c-d. Three and a half inches long. Surinam. Purchased of Mr. 



Frank. 

 e. Three and a half inches long. Maranon. 



