NATURAL SCIENCES OF PHILADELPHIA. 69 



On the Cranial Characteristics of GADUS PROXIMUS Grd. 

 BY THEODORE GILL. 



While engaged in the investigation of the comparative anatomy of the 

 Gadoids and allied families, my attention was arrested by the very distinctive 

 characters exhibited by the Californian Gadoid named by Girard Gadus prox- 

 imus or Morrhua proxima. The title of that form to generic separation from 

 the typical Gadi, is fully confirmed. I may remark, that I had long distrusted 

 its pertinence to Gadus on account of its small size, but the few and trivial 

 outward peculiarities exhibited by it, almost forbade a separation, until more 

 should be known concerning its organization. 



The affinities of the new genus are, perhaps, rather with Brachygadus than 

 Gadus itself; but the form of the head sufficiently distinguishes it from thai 

 type. The distinctive external characters are the angular form of the fins, 

 especially of the first dorsal, the small size and the immaculate body. All 

 the osteological characters, herewith given, are contrasted with those of 

 Gadus, and the peculiarities are indicated by the italicized portions. 



If, as I suspect, the Gadus pygmaus of Pallas belongs to Boreogadus, as 

 restricted by myself, at least three genera of Gadinoz are represented along 

 the western American coast. 



MICROGADUS Gill. 



The cranium is proportionally broader towards the front and less flattened, 

 while the brain case is flattened below, decidedly swollen laterally and on each 

 side of a depressed sphenoidal groove, and has an ovate cordiform shape. 

 The paroccipital or epiotic is not produced into an angle behind, but is ob- 

 tusely rounded, and its posterior or outiuardly descending ridge blunt. The pe- 

 trosal or opisthotic is well developed, oblong, and with its re-entering angle 

 high up, and, on a line with it, the surface is divided into two parts ; an upper 

 narrow and flattened one, and a lower expanded one, much swollen ; the 

 alisphenoid or pro-otic is oblong, acutely emarginated in front, swollen from 

 the region of the high anterior sinus, and above it little produced forwards. 

 The great frontal is little longer than broad, with supraoccipital crest continued 

 only along its posterior third, but an anterior low crest continued forwards on 

 the bone, and near the front expanded upwards, and with the expanded por- 

 tion behind dividing into narrow lateral wings ; the lateral tectiform ridges of 

 the frontal are continued forwards and curved outwards towards the antero- 

 lateral angles. The anterior frontals are mostly covered in front by he great 

 frontal, and are much developed in the direction of the antero-lateral angles ; 

 the inferior expanded axillar portion being very narrow. The nasal has a 

 rounded ridge in front continued well below, and its posterior crest is laminar" 

 and trenchant. 



The rest of the bones offer less decided peculiarities, and, therefore, their 

 immediate consideration is less requisite. 



Gadus tomcodus Mitchill exhibits similar modifications of the cranium, and 

 should be approximated to G. proximus. 



Note on several Genera of CYPRINOIDS. 



BY THEODORE GILL. 



As considerable misapprehension appears to have prevailed regarding several 

 genera of Cyprinoids, established for forms characteristic of the Pacific slope of 

 North America by Girard, due, perhaps, to the vague or erroneous ideas enter- 

 tained by that gentleman himself, it may be advisable to give the partial 

 results of a renewed examination. 



1865.] 



