230 



U. S. p. E. R. EXP. AND SURVEYS — ZOOLOGY — GENERAIi REPORT. 



5. DIONDA GRISEA, Grd. 

 Plate LII, Figs. G— 10. 



Spec. Char. — Body rather deep upon its middle; greatest dcptli nearly equal to the length of the head. Head sub-conical and 

 slender, contained five times and a half in the total length ; snout tapering ; gape of mouth nearly horizontal, its angle being far 

 from reaching a vertical line drawn in advance of the orbit. Eye moderate, sub-circular. Caudal fin entering nearly five 

 times and a half in the total length. Insertion of ventrals situated somewhat posteriorly to the anterior margin of the dorsal. 

 Scales moderate sized, deeper than long. Reddish asli above ; olivaceous beneath ; fins unicolor. 



The species is closely allied to D. plumbea and J), punicea, differing from both of them by a 

 more slender and tapering head ; the snout being, however, blunt as in all the species of the 

 same genus. The diameter of the eye enters four times in the length of the side of the head. 

 The scales are very different from those of B. punicea, in being deeper than long, in which 

 respect they resemble more those oi D. plumbea, from which they maybe distinguished in being 

 less tapering posteriorly. 



The color is of a uniform reddish ash above ; yellowish or olivaceous beneath ; the fins being 

 unicolor. 



Iteftrences to the figures. — Plate LII, fig. 6, represents Dionda grisea, size of life. Fig. 7 is a 

 section of the body across the line of greatest depth. Fig. 8, a dorsal scale. Fig. 9, a scale 

 from the lateral line. Fig. 10^ a scale from the abdominal region. 



List of specimens. 



HYBORHYNCHUS, Agass. 



Gen. Char. — Head rather short, upper surface depressed ; snout abruptly truncated and rounded. The mouth is of medium 

 size, subterniinal, its gape being horizontal, the lower jaw flattened and thin, rounded upon its periphery and slightly overlapped 

 by the snout. The angles of the mouth do not reach a vertical line drawn in advance of the orbit. The eyes are large ; the 

 isthmus is of moderate width. Anterior ray of dorsal fin shorter than the second. The insertion oftho ventrals is situated 

 opposite the anterior margin of the dorsal, in advance or posteriorly to it. The caudal is furcated. The scales are large, 

 higher than long, with radiating furrows upon their posterior section only ; tlic lateral line follows the middle of the flanks. 

 The phary.'geal bones arc slender, and more so upon the inferior limb, which is longer than the upper and curved backwards 

 and sideways, whilst the upper limb is gently curved inwards. The convexity of the same bone is expanded. The tectli are 

 of the cultriform kind of the grinding type, very much compressed, slightly hooked, and consequently provided with quite a 

 narrow grinding surface. Their disposition is upon a single row of four : 4—4. 



Sis.—lhjhorhynchvs, Agass. in Amer. Journ. of Sc. i2d ser. XIX, 1855, 222.— Grd. in Proc. Acad. Nat. Sc. Pliilad. VIII, 

 IWG, 179. 



The species of this genus, like those of the preceding one, are, generally speaking, of small 

 size^ not exceeding four inches in total length. H. notatus is the largest of the hitherto known 

 species, and we regret that both space and time did not permit its being included m this report. 



