188 



U. S r. R R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



List of specimens. 



RHACOCIIILUS, Agass. 



Gen. Char. — Head of medium size. Mouth moderate, nearly Iiorizontal, with both jaws equal. Lips very fleshy, lower one 

 broad, lobed, and free all around. Premaxillaries very protractile. Teeth few, on the anterior ptirtion of the jaws only, and 

 disposed upon one single row. Spinous portion of dorsal fin lower than the soft. Anterior articulated rays of anal fin simple 

 and preceded by three small spines. Caudal deeply forlteJ. Scales rather well dsveloped ; lateral line concurrent witli the 

 dorsal outline. No scales upon the fins. Dorsal groove occupying the middle of the fin ; slieath formed by two rows of scales. 



Stn. — Rhacochilus, Agass. in Amer. Journ. of Sc. 2d series, XVII, 1854, 367. 



As the name implies, the lower lip, which is free all around, is fringed or rather cut up upon 

 its margin. The genus is allied to Emhiotoca by its dentition and the outline of the dorsal fin, 

 differing principally from it by the lower lip not being attached to the symphysis of the jaw, 

 and by the indentations of its margin. The protractility of the snout is much greater also than 

 in Emhiotoca, but not more so than in Holconotus. Like Emhiotoca, however, this genus exhibits 

 a patch of large scales, isolated amongst the rest, towards the lower portion of the abdomen, 

 though placed further back. 



RHACOCHILUS TOXOTES, Agass. 

 Plate XL. 



Spec Char. — General form of body sub-elliptical in profile ; nape prominent, frontal lino very declivous. Eye large and 

 circular. Posterior extremity of maxillary extending to a vertical line drawn inwardly of the anterior rim of the orbit. Base 

 of anal fin (spinous rays e.vceptcd) nearly equal to the base of soft portion of the dorsal. Color, uniform olive above; sides 

 silvery with liijht longitudinal streaks. Pectorals, dorsal, and caudal dark greyish olive ; anal and ventrals dark jiurple. 



SvN. — Rliacocliiliis loxotes, Agass. in Amer. Journ. of Sc. 2d. ser. XVII, 1854,367. — Grd. in Proc. Acad. Nat. Sc. 

 Philad. VUI, 1856, 136. 



The general form of the body is sub-elliptical in profile, the nape being prominent and the 

 frontal line very declivous, with an occipital depression. The outline of the back, as well as 

 that of the belly, is regular and rather sub-depressed ; along the insertion of the anal the outline 

 is rather straight and ascending. The peduncle of the tail is thickish. 



The head is of but moderate development, it being contained four times and a half in the 

 total length ; it is a little deeper tiian long upon the line of its greatest deptli, which is the 

 occipito-hyoid. The eye is large and circular, its horizontal diameter being contained about 

 four times in the length of the side of the head, and more than once in advance of its anterior 

 margin. The snout is very protractile downwards, and when retracted it is rounded or sub- 

 truncated, terminated by very thick and fleshy lips ; tlie inferior one being free all around and 

 presenting three indeatations upon its margin : a median, opposite the symphysis of the jaw, 

 and two somewhat smaller, lateral, one on each side. The teeth are buried in the thickness of 



