21. PSEUnOCHALCEUS. 331 



20. SCISSOR. 



The dorsal fin is placed nearly in the middle of the length of the 

 body, above the interspace between ventrals and anal ; anal iin long. 

 Body oblong, covered with scales of moderate size ; lateral line con- 

 tinuous ; belly rounded. Cleft of the mouth wde ; intermaxillary 

 and mandibular}' teeth as in Tetrcuionopterua; maxillary hone toothed. 

 Nostrils and gill-opening as in Tctruffonopterus, Gill-rakers short, 

 lanceolate. 



South America. 



This genus is closely allied to Tetracjonopterus, but has a very dif- 

 ferent physiognomy, and the gill-rakers are not setiform, as in that 

 genus. 



1. Scissor macrocephalus. 

 B. 4. D. 11. A. 29. V. 8. L. lat. 38. L. transv. 7/6. 



The height of the body is contained thrice and one-fourth in the 

 total length (-ndthout caudal), the length of the head thrice and one- 

 third ; head two-thirds as high as long ; nape of the neck abruptly 

 elevated behind the occiput. Interorbital space somewhat convex, 

 its width being equal to the diameter of the eye, which is less than 

 one-fourth of the length of the head. Snout conical, longer than 

 the eye, with the lower jaw prominent. The maxillary is long and 

 narrow, slightly dilated posteriorly, extending to beyond the anterior 

 margin of the eye. Teeth rather strong, pointed, indistinctly tri- 

 cuspid : those of the outer series of the intermaxillary are smaller 

 than those of the inner ; mandibidary teeth strongest, the two middle 

 ones -widely apart, to receive a pair of the upper jaw between them ; 

 the upper half of the maxillary is armed with very small conical teeth. 

 The origin of the dorsal fin is nearer to the base of the caudal than 

 to the end of the snout, the fin occupying exactly the middle between 

 ventral and anal ; its height is two-thirds of the length of the head. 

 Anal fin rather low. Caudal forked to its base, with the lobes equal, 

 their length being two-thirds of tlie length of the head. The por- 

 tion of the tail behind the anal is somewhat longer than deep. The 

 pectoral extends a little beyond the root of the ventral ; the ventral 

 to the vent. Body uniformly coloured, shining silvery ; a blackish 

 band on the root of the caudal fin and along its middle raj"S. 



rt. Six inches long. Purchased of Mr. Frank. 



This specimen was received without any information as to the 

 locality whence it was obtained, but as all the specimens from the 

 same source were from Surinam, it is probable that this species also 

 comes from that country. 



21. PSEUDOCHALCEUS. 

 Pseudochalceus, Kmr, in Sitzffsher. Acad. Wiss. Miiiich. 180.3, p. 225. 

 " Dentcs intermaxiUares biscriales, cuspidati, duo medii majores: 

 maxillares simplices, acuti, uniseriales ; dentcs inframaxillarcs uni- 



