64 PROCEEDINGS OF THE ACADEMY OP 



deeper than long, rounded off, broader anteriorly than posteriorly, exhibiting 

 distant concentric lines of growth and very wide radiating furrows which 

 affect the anterior portion of the scale only. The head is scaleless, but its 

 upper surface as well as its sides, exhibit transverse cutaneous, finely granu- 

 lar ridges. A few of the latter may be observed along the flanks, over the 

 scales, although much less conspicuous than on the head. The color is a 

 uniform dull yellowish white tint. 



XIV. The "sun fish," which we have formerly described under the name 

 of Promotis obesus, * belongs now to the genus Bryttus, as characterized in our 

 Report upon the Fishes of the U. S. P. R. R. Explorations and Surveys. Its sys- 

 tematic name, therefore, will be henceforwards Bryttus obesus. 



XV. While assorting some of the fishes which the Smithsonian Institution 

 had been receiving during the past years, a specimen of the genus Megalops 

 was found in one of the kegs sent from the Tortugas, Garden Key, Fla., by 

 Lieut. H. G. Wright. It belongs to the same species as that which we have 

 formerly described under the name of M. elongatus. 



It is three feet and three inches long, regularly subfusiform in its profile 

 the head constituting the fifth of the total length. The greatest depth, which 

 is seven inches, corresponds to the anterior portion of the body, nearly mid- 

 way between the pectoral and the ventral fins. The posterior extremity of 

 the maxillar bone extends considerably beyond a vertical line which would 

 intercept the hind rim of the orbit. The eyes are subcircular, their diameter 

 entering five times in the length of the side of the head. 



The anterior or external ray of all the fins is very stout, considerably stouter 

 than the other rays, and usually the longest also. By anterior or external 

 ray is understood that which begins the series of developed rays, and not the 

 rudiments of rays that occur at the anterior or external margin of the fins. 

 The pectoral fins are lanceolated, but their extremity does not extend as far as 

 the origin of the ventrals. The latter are inserted altogether in advance of 

 the dorsal, so that when expanded, their posterior edge, which is linear, will 

 meet a vertical line dropped from the origin of the dorsal. The caudal is 

 deeply furcated and somewhat shorter than the head. The anal is longer than 

 deep, exteriorly concave or crescentic, the posterior rays extending further 

 back than the posterior, very elongated ray, of the dorsal fin. The latter is 

 much higher than long, somewhat concave upon its upper margin. There 

 are ten longitudinal series of scales between the dorsal and the ventral fins. 

 The total number of scales upon a girdle encircling the body in advance of the 

 insertion of the ventrals being also its greatest depth is twenty two, ten on 

 either side, and two odd series, a dorsal and an abdominal series. Small scales 

 may be observed upon the anal and caudal fins to near the extremities of their 

 rays. The numbers of the rays in the various fins correspond to those already 

 given ; we need but to state that those of the caudal may thus be expressed : 

 C 4, 1, 9, 9, 1, 3, giving twenty developed rays and nine, perhaps more, rudi- 

 mentary ones. 



XVI- The brooks and streams which mingle their waters with that 

 of the Potomac river have furnished us with a representative of the Ethe- 

 ostomid family, of an apparently new generic type, the characters of which 

 may be thus expressed : body subfusiform ; head subconical ; snout rather 

 blunt, the upper jaw protruding beyond the lower one, thus giving the mouth 

 an inferior position. The latter is of moderate size, its gape nearly horizontal, 

 surrounded with conspicuous lips. Opercular apparatus scaly, cheeks and 

 throat bare. Dorsal fins distinct ; first dorsal lower than the second, and longer 

 than high. Anal smaller than the second dorsal. Caudal fin posteriorly trun- 

 cated or subtruncated. The genus we will call Arlina. 



* Proc. Bost. Soc. Nat. Hist. v. 1844, 40. 



[Feb. 



