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



back and belly being arched. The greatest depth is about a third of the length ; the peduncle 

 of the tail is slender and short. 



The head is sub-conical and rather pointed forwardly. It is sliglitly depressed above the 

 orbit, otherwise its profile would form a regular curvilinear prolongation of the dorsal outline. 

 The mouth is rather small, the premaxillaries moderately protractile, and the lower jaw 

 projecting slightly beyond the upper when the mouth is partially open : otherwise the jaws 

 may be termed equal, the gape of the mouth being somewhat oblique when both jaws are in 

 a retracted state. The posterior extremity of the maxillary does not quite reach a vertical line 

 passing immediately in advance of the orbit. The teeth are of medium development, sub- 

 conical or slightly club-shaped, and occupying the entire circumference of the mouth. On the 

 inner row of the upper jaw they are often so small as to defy observation. The nostrils are 

 nearly equal, situated towards the upper surface of the snout, a little nearer the anterior 

 rim of the orbit than the extremity of the snout. The eye is proportionally large, circular 

 in shape, and its horizontal diameter contained somewhat less than four times in the length of 

 the side of the head, exactly once between the orbit and the end of snout, and a little less than 

 twice between the orbit and the thoracic belt. There are three rows of irregularly imbricated 

 scales on the cheeks, and four or five on the opercle. The branchiostegal rays, five on either 

 side, are small, and concealed under the opercular apparatus. 



A vertical line drawn from the origin of the dorsal fin passes immediately behind the base of 

 the pectorals. Nine or ten rays constitute the spinous portion, gradually higher from the first, 

 which is the lowest of all, to the fourth or fifth, which is the highest ; thence diminishing 

 again to the last, which is a little shorter than the first articulated ray. The remaining portion 

 of this fin occupies a base nearly double the length of that over which the spines extend. The 

 articulated rays are very slender, and bifurcate but once beyond the half of their depth. The 

 caudal fin is deeply forked, and its rays sub-divide three times upon their length. The anal 

 is long and low, provided anteriorly with three small spines. The anterior articulated rays 

 are not all divided : from four to eight in the female, and six to eleven in the male, are simple ; 

 the rest bifurcate once, as in the caudal fin. In the male the simple and divided rays are 

 separated by a triangular space, the undivided ones inclining anteriorly, the bifurcated 

 posteriorly. The origin of the anal is opposite the fifth articulated ray of the dorsal, and 

 extends a little more posteriorly than the latter. The origin of the ventrals is placed under 

 the vertical line of the second or third dorsal spine. The external spine is slender and acute ; 

 the articulated rays sub-divide three times. The pectorals are well developed, their extremity 

 reaching the vertical of the second articulated ray of the dorsal, and a little beyond the tips of 

 the ventrals themselves. Partial traces of a bifurcation of the third degree may be observed 

 towards the extremities of their rays. 



Formula of the fins : 



Br.V: V; $ D IX or X, 20 or 21 ; A III, 8 -f 14 = 22 ; C 3, 1, 6, 6, 1 2 ; V I, 5 ; P 19. 

 9 D IX or X, 19 or 20 ; A III, 11 + 13 = 24 ; C 3, 1, 6, 6, 1, 2 ; V I, 5 ; P 18 or 19. 



The scales are proportionally large ; about four rows may be counted above the lateral line 

 and twelve beneath it. The lateral line itself contains from forty to forty-four scales, and runs 

 nearly parallel to the outline of the back. The dorsal groove extends from the highest dorsal 

 spine to about the middle of the length of the articulated portion of the same fin. The sheath 



