238 



U. S. p. R K. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



of the tail to the caudal fin. The epecimen figured and described is twelve inches and a half 

 in total length. 



References to the figures. — Plate LIII, fig. 1, represents Orthodon niicrolepidotus, somewhat 

 reduced in size. Fig. 2, a scale from the dorsal region. Fig. 3, a scale from the lateral line. 

 Fig. 4, a scale from the abdominal region. 



List of specimens. 



ALGANSEA, Girard. 



Gen. Char. — The head is sub-conical, more or less pointed, though rounded upon its periphery. The mouth being of medium 

 size, slightly oblique upwards, its angles never extending beyond the anterior rim of the orbit; the jaws themselves terminate 

 evenly. The eye is of moderate development. There is a narrow isthmus between the gill openings. The body short and 

 stoutish, quite compressed, covered with scales of medium or of large size, the lateral line being sub-medial, slightly deflexed npon 

 the middle of the abdomen. The fins are rather moderate in development ; the origin of the ventrals is situated opposite to 

 the anterior margin of the dorsal, the posterior margin of the latter never reaching the anterior margin of the anal. The caudal 

 fin is emarginated posteriorly. The pharyngeal bones are moderately strong ; the upper and lower branches nearly of equal 

 strength, though the lower is somewhat longer than the upper. The convexity is strongly marked and dilated. The teeth are 

 of the cultriform kind of the grinding type, disposed upon a single row of four or five, as follows : 4 — 4 or 5 — 5. The uppermost 

 stand boldly out above the surface of the bone. 



S\ti.—Alijansea, Grd. in Proc. Acad. Nat. Sc. PhUad. VUI, 1856, 182. 



The typical species of this genus {A. tincella) is Mexican ; it is figured and described in the 

 Report of the United States and Mexican Boundary Commission. It differs widely from the 

 three following species found within the limits of the United States. 



1. ALGANSEA BICOLOE, Grd. 



Spec. Char. — Head contained four times and a half in the total length. Eye of moderate size : its diameter entering four 

 times and a half in the length of the side of the head. Posterior extremity of the maxillary e.xtendinj^ to a vertical line drawn 

 across the nostrils. Anterior edge of dorsal fin nearer the insertion of the caudal than the extremity of the snout. Insertion 

 of ventral fins is somewhat in advance of the anterior margin of the dorsal, and nearer the base of the caudal than the extremity 

 of the snout. Scales large. Back and sides of a metallic bluish black tint, intermingled, upon the lower half of the flanks, 

 with a golden hue. The inferior region is pure wliite or yellow. Fins bluish grey at their base, olivaceous at their periphery. 



Syn. — Algansea bicolor, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 183. 



The body is thickest anteriorly, and tapers backwards ; the nape is slightly swollen. The 

 head enters about four times and a lialf in the total length. The ventrals are inserted a little 

 in advance of the anterior margin of the dorsal. Of all the species hitherto known of this 

 genus, the one here referred to has the largest scales, five rows of which may be counted from 

 the origin of the ventrals to the lateral line, and nine from the lateral line to the anterior 

 margin of the dorsal : in all fifteen rows. They are deeply imbricated, nearly as deep as long, 

 anteriorly sub-truncated, with a few radiating grooves upon their posterior section only. The 

 rays of the fins are as follows : 



D 1, 9 ; A 1, y ; C G, 1, 9, 8, 1, 7; V 9 ; P 16. 



