120. GADIDvE GADUS. 805 



tebrse, resembling the structure found in Merlucius. This difi'erence, in 

 Dr. Beau's opinion, may necessitate the revival of the genus Tilesia of 

 Swaiuson. 



(Gadus gracUis Tilesius, Mem. Acad. Imp. St. Petersb. ii, 354, 1810: Gadus wact>na 

 Pallas, Zoogr. Ross.-Asiat. Hi, 182, 1811: Tilesia gracilis Swainsou, 1. c. : Tilesia yracilis 

 Bean, Proc. U. S. Nat. Mus. 1881, 243). 



l)b. Vent in front of second dorsal; species of small si/e. (Microgadus* Gill.) 



1341. G. proximus Grd. Tom-cod. 



Olivaceous above, pale, or slightly translucent, white below; dorsal 

 fins dusky, paler at base; first anal, and veutrals uucolored; second 

 anal dusted with dark points. Head long, convex above, somewhat 

 compressed, with vertical sides; eye moderate, about 5 in head; mouth 

 rather large; maxillary reaching to below pupil; barbel small; teeth 

 in each jaw in a baud, the outer row a little enlarged. Gill-membranes 

 ajittle connected, free from the isthmus. First dorsal highest, some- 

 what falcate, its height three-fifths length of head; first anal longer 

 and higher than second; pectorals moderate, reaching anal; ventrals 

 filamentous, scarcely reaching anal ; caudal slightly emarginate. Lat- 

 eral line very distinct, wavy, high anteriorly, slightly interrupted pos- 

 teriorly. Vent below first dorsal. Head 4; depth 4f. D. 14-18-19; 

 A. 21-21; V. 6 or 7. L. 1 foot. Monterey to Alaska ; abundant; a 

 food-fish of some importance. 



The Tom-cods (Microgadus} differ considerably from the true cods 

 (Gadus) in the structure of the cranium. The following is Professor 

 Gill's account of the skull of G. proximus, the italicised portions indi- 

 cating the differences from Gadus callarias : 



"The cranium is proportionally broader towards the front and less 

 flattened, while the brain -case is flattened below, decidedly swollen on 

 each side of a depressed sphenoidal groove, and has an ovate cardi- 

 form shape; the paraoccipital or epiotic is not produced into an angle 

 behind, but is obtusely rounded, and its posterior or outwardly-descend- 

 ing ridge Hunt; the 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 a narroic and flattened one, and a lower expanded 

 one, much swollen; the alispheuoid or pro-otic is oblong, acutely eniar- 

 giuate in front, swollen from the region of the high anterior sinus, 

 and above a little produced forwards; the great frontal is a little longer 



*Gill, Proc. Acad. Nat. Sci. Pliila. 1865, 69: type Gadus proximus Grd. 

 small; yadoe, Gadus.) 



