1886.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 327 A REVIE-W OF THE SPECIES OF THE GENUS PRIONOTUS. By DAVID !^. JORDAN aii«l ElilZABETH O. HVOHES. In the present paper we have giveu the sjiionymy of the species of Prionotus, or Sea Eobius, together with an analytical key by which they may be distingnished. The material examined by us is chiefly in the museum of the Indiana University, having been collected mostly hy Professors' Jordan and Gilbert and i\lr. Silas Stearns. Most of the characters in the following analysis have been taken from adult specimens. Young exam[)les in most cases diflerfrom the adults in the following respects, in addition to those characters which usually distinguish young fishes : The spines on the head are sharper, more conspicuous, and more com-pressed in the young, and some spines, especially those on the side of the head, disappear entirely with age. The interorbital space is more concave in the young. The pectoral fins are also much shorter. The gill-rakers are longer in the young, and proportionately more slender, and some of the color markings — especially the dark cross-shades — are more conspicuous, while the spots on body and fins are less so. The following is the synonymy of the genus. PRIONOTUS. Prionotus Lacfepfeide, Hist. Nat. Poiss. Ill, 37, 1802 (evolans). Ornichthys Swainsou, Nat. Hist. Classn. Fishes, II, 1839, 262 (punctatua). Chriolax Jotclau & Gilbert, Proc. U. S. Nat. Mus., 1878, 374 (evolana). Type Prionotus evolans L. The species of Prionotus so far as known are confined to the waters of America and Japan. They may be compared as follows: ANALYSIS OF THE SPECIES OF PRIONOTUS. a. Dorsal rays VIII to X — 11 to 13. Anal rays 11 or 12. 6. Mouth comparatively small, the maxillary less than one-third the length of the head, the mandible not extending backward as far as the vertical from the front of the eye ; a more or less distinct cross-groove* on top of head behind eye ; black spot on spinous dorsal very distinct, ocellated, confined to the membrane between fourth arid fifth spines. 0. [Pectoral fins very long, reaching base of caudal, the rays graduated, the ninth the longest ; scales small, in 109 transverse series, 50 tubes in the lateral line ; gill rakers short-ish, 1+6 in number; body rather htout, the depth 4 in length; palatine teeth few, feeble; caudal sub-truncate ; second dorsal spine longest, half the length of head ; first spine strongly serrated in front ; pre-*Not described in P. aJatus, but probably present.