282 



U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



The dorsal region is light reddish brown and yellowish white beneath ; the middle of the 

 flanks is silvery. The fins being unicolor, of a light olive. 



List of specimens. 



3. LUXILUS LUCIDUS, Grd. 

 PLATE LX, FIGS. 912. 



SPEC. CHAR Body rather elongated, sub-fusiform in its outlines. Head moderate sized, contained five times in the total 

 length. Snout sub-conical, tapering ; gape of the mouth somewhat oblique ; posterior extremity of maxillar bone extending to 

 a vertical line drawn in front of the orbit. Eye well developed ; its diameter entering three times and a half in the length 

 of the side of the head. Anterior margin of dorsal fin somewhat nearer the tip of the snout than the insertion of the caudal. 

 Greyish brown above ; yellowish beneath. Fins unicolor, assuming the tint of the region to which they belong. 



SYN. Luxilus lucidus, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 203. 



The general form resembles that of L. seco. The head, however, is contained but five times 

 in the length of the side of the head. The mouth is a good deal larger, whilst the eye is 

 smaller. The dorsal fin is much higher than long ; its upper edge being sub-convex. The 

 anal is but a little deeper anteriorly than long ; its lower edge is sub-concave, and its anterior 

 margin nearer the fork of the caudal than 1he isthmus. The caudal itself is somewhat longer 

 than the head,, hence it is contained short of five times in the total length. The origin of the 

 ventrals is nearer the extremity of the snout than the insertion of the caudal ; their posterior 

 edge is rounded off, or sub-convex, and their tips overlap the vent without reaching quite the 

 origin of the anal. The pectorals are sub-lanceolated ; their extremities not extending as far 

 as the insertion of the ventrals. The following formula gives the number of the rays of the 



various fins. 



D 2, 8 -f 1 ; A 2, 10 -f- 1 ; C 9, 1, 8, 8, 1, 10 ; Y 8 ; P 12. 



The scales are rather large, very much deeper than long, anteriorly sub-truncated, posteriorly 

 rounded, and tapering superiorly and inferiorly. The radiating furrows are but few and 

 occasionally obsolete. The lateral line being very much deflexed upon the abdominal region. 



The upper region is greyish brown, whilst the inferior region is yellowish, else of a dull 

 whitish tint. The middle of the flank somewhat metallic white. The vertical fins are greyish ; 

 the ventrals and pectorals being yellowish. 



^References to the figures. Plate LX, fig. 9, represents Luxilus lucidus, size of life ; fig. 10 is 

 a dorsal scale ; fig. 11, a scale from the lateral line ; and, fig. 12, a scale from the abdominal 

 region. 



List of specimens. 



