FISHES— OPIIIDIDAE—AMMODYTES PEKSONATUS. 
139 
AMMODYTES PEKSONATUS, G- r d . 
Spec. Char.— Head constituting about the fifth of the total length. Posterior extremity of maxillary extending to the 
anterior rim of the orbit. Eyes rather large. Origin of dorsal fin situated in advance of the extremities of the pectorals. 
The caudal fin is posteriorly sub-crescentic. Greyish brown above; silvery beneath ; base of caudal, black. 
Syn.— Jlmmodytespersonatus , Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 137. 
The head, which is sub-conical and pointed, constitutes the fifth of the total length ; the 
largest specimen before us measuring four and a half inches. The gape of the mouth is some¬ 
what oblique owing to the protraction of the lower jaw beyond the upper one ; the posterior 
extremity of the maxillar hone corresponding to a vertical line intersecting the anterior rim 
of the orbit. No teeth on either jaw; none on the vomer and palatine bones. The eye is large 
and circular ; its diameter entering about five times in the length of the side of the head. The 
branchial apertures are very wide, and the opercular apparatus largely developed; the sub and 
interopercle being nearly equal to the opercle, the free edge of the sub-opercle extending 
considerably beyond that of the opercle. Radiating striae or ridges may he observed on the 
preopercle and interopercle. The branchiostegals are elongated and slender, seven on either 
side. 
The body is compressed, deeper than broad, the dorsal and abdominal regions rounded, 
diminishing gradually backwards in depth and width both. 
The dorsal fin, the origin of which is placed at an inch from the tip of the upper jaw, in a 
specimen measuring three inches and seven-tenths, is nearly of equal depth throughout its 
whole length ; the tip of its posterior rays, when bent backwards, do not quite reach the 
insertion of the caudal fin. Its rays being slender and not bifurcated. The caudal fin enters 
about eleven times in the total length ; its posterior margin is sub-crescentic and its medial 
rays bifurcated. The anal fin is less than half the length of the dorsal, being posteriorly even 
with the latter, hence its origin placed backwards of the middle of the dorsal. It is deeper 
anteriorly than posteriorly, and where deepest it is deeper than the dorsal, whilst its depth 
behind is equal to the height of the dorsal opposite. Its rays are likewise slender and not 
bifurcated. The pectorals, which are inserted near the lower part of the thoracic belt, are 
moderate sized, rather elongated, composed of both simple and bifurcated rays, the bifurcated 
ones occupying the middle of the fins. When brought alongside the body their posterior 
extremity extends considerably beyond a vertical line drawn at the origin of the dorsal. The 
absence of the ventrals is a trait peculiar to the family to which the species belong. 
Br. VII: YII; D 55 ; A 25 ; C 3, 1, 7, 6, 1, 4 ;. V —; P 14. 
The vent is placed near the anterior margin of the anal fin. 
The scales, which are disposed upon transversely oblique series, are deeper than long, 
provided all around with wide radiating furrows. The lateral line begins opposite the posterior 
angle of the opercle, and takes a straight course to the peduncle of the tail along the line of 
intersection between the dorsal muscles and the lateral myocomma. The flanks exhibit a 
shallow groove, parallel to the vertebral column, and intersecting the middle bent of the lateral 
myocomma. 
Finally, another similar groove extends from under the pectorals to the peduncle of the tail, 
along the line of intersection between the abdominal muscles and the lower extremities of the 
