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 



