242 



U. S. p. R. R. EXP. AND SUKVEYS — ZOOLOGY GENERAL REPORT. 



2. LAYINIA HARENGUS, Grd. 



Spec. Char. — Body compressed, sulifusirorm in profile, and gradually tapering towards the peduncle of the tail. Head 

 constituting the si.xtli of the total length ; diameter of the eye entering about five times in the length of the side of the head. 

 Moulh moderate ; posterior extremity of maxillar bone, nearly even with a vertical line drawn before the orbit. Anterior 

 margin of dorsal fin nearer the base of the caudal than the extremity of the snout. Insertion of ventrals nearly equidistant 

 between the extremity of the snout and the base of the caudal fin. Cauda! moderately furcated. 



Stn — Lavinia harengus, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 184. 



This species is intermediate between L. exilicauda and L. alutacea. The most characteristic 

 feature consists in the general shape of the body and the relative position of the dorsal and anal 

 fins, which are wider apart. The size of these fins being nearly the same, and if any appreciable 

 difference be observable, the anal would be found somewhat larger than the dorsal. The 

 number of the rays in the various fins is as follow : 



D 1, 10 ; A 2, 10 ; C 9, 1, 9, 8, 1, 8 ; V 1, 10 ; P 16. 



The dorsal and anal are the only fins presenting difierences of some specific value. The 

 specimens before us are in a mutilated condition, inasmuch as the scales are all fallen. The 

 dorsal region seems to have been of a much deeper hue than the lower half of the sides, which 

 are whitish, as well as the belly, contrasting with the rather dark hue of the dorsal region. 



List of specimens. 



TRIBE OF POGONICHTHI. 



This fourth group is less uniform, if the teeth are taken into account. The latter belong to 

 the hooked types, with or without grinding surface {Denies uncinato-svhmolares and uncinafo- 

 suhconici), of the raptatorial (Denies raptatori) and prehensile (D. prehensiles) kinds chiefly ; in 

 most cases disposed upon a double series. But all its representatives are provided with buccal 

 or maxillar barbels ; and the upper jaw, in projecting more or less beyond the lower, gives the 

 mouth an inferior position, although not so decided as in the group of Catostomi, except in some 

 species of the genus Argyrevs, in which the snout is rather elongated and conical, and which 

 suggested the name of lihinichlhys. In the species from the Pacific range, a thin cartilaginous 

 pellicle is observed upon the jaws : illustrating what has already been stated, that the cartilagi- 

 nous lips are not sufficient to characterize the group of Chondrostomi. Of course, it is in the 

 latter where that character assumes its greatest development. 



This group or tribe was distinguished for the first time, without any name being affixed to it, 

 in the "Proc. of the Acad, of Nat. Sc. of Philad. VIII, 1856, 184." 



