NATURAL SCIENCES OF PHILADELPHIA. 233 Gen. Char. Bill shorter than the head, compressed, exceedingly stout, obtuse at the end ; culmen straight to the nostrils, then very convex to the decurved and acute tip of the upper mandible. Commissure slightly sinuate at the base, straight to near the tip, where it is suddenly deflected. Gonys regularly convex, the angle scarcely appreciable. Upper mandible covered with soft skin from the base to the nostrils, between which are two fossae, the an-terior shallow and oblong, the posterior triangular and deep, opening into the bare loral space ; the two separated by an oblique ridge. Nostrils situated near the extremity of the anterior fossa. Outer three or four primaries ab-ruptly attenuated near the end. Tarsus much abreviated, comparatively stout, about three-fourths the middle toe and claw. Middle and outer toe nearly equal. Lobes of toes broad, connected at base for a greater distance than in other genera. 1. Podilymbps podiceps (Linn.) Colymbus podiceps. Linn., 1766. Podilymbus pod. Lawr., 1858. Podil. lineatus, Heerm. , 1S54. Colymbus ludovicianus, Gruel., 1788. Podiceps ludov. Lath., 1790. Pod. carolinensis, Lath., 1790. Sylbeocyclus carol., Bon., 1838. Habitat. Continent of North America. On a new genus of Fishes allied to AULORHYNCHTJS and on the affinities of the Family ATJLORHYNCHOIDJE, to which it belongs. BY THEODORE GILL. In the Proceedings of the Academy of Natural Sciences for July, 1861, (p. 168), I have described a new type of fishes, and referred it to the family of Aulostomatoids, with which it agreed in the elongation of the body, form of the head, opposition of the dorsal and anal fins and the development before the former of free spines as well as the presence of four branchiostegal rays. In the MSS. remarks on the relations of the genus, intended for the Report on the Fishes collected by the Northwestern Boundary Commission, I had commented on the relations of the new form and its affinity to the Gasterostoid genus Spinachia. I have now the pleasure of making known a genus which is still more closely related to Spinachia, and which it would not be even very improper to refer to the family of Gasterosteoids. It has, however, the four branchiostegal rays of Aulostoma and Solenostomus, as well as the more elongated tube. But I am disposed to believe that the four subfamilies* of the Aulostomatoid fishes proposed in my former paper, are true families, and that Aulorhynchus, and especially the new genus are at least as closely related to the Gasterosteoids as to the Aulostomatoids. They agree with the former family in 1st. General form. 2d. Development of the dorsal and anal fins and the antecedent spines. 3d. Development of the forearm (ulnar and radial bones) and of the pectoral fin. 4th. Position of the ventral fins. 5th. De-velopment of the caudal fin. The affinity of the two families is further shown by the possession of other characters in common by the Spinachianse and Aulichthys. * The genus Siphonognathus of Richardson appears to be the type of a peculiar family (Siphognathoidae), more nearly related to ihe Labroids than to Ihe typical Aulostomatous fishes, although havisg the four branchiostegal rays, tubular snout, &c. of the latier. Dr. Gunther has first perceived its affinities, but appears to be wrong in referring it to the same family with the other Labroids. 1862.] 16
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