140 



U. S. p. R. R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



lateral myocomma. This groove is, moreover, furnished with a thin though opaque membrane, 

 which gives it the appearance of a ridge, especially along the abdominal region, where it is 

 more developed than further behind. 



The dorsal -region is greyish brown ; the lower half of the sides and the belly being silvery ; 

 the base of the caudal is black. 



SUB-ORDER II. 



THORACIC!. 



The ventral fins being present, they are inserted under the thoracic belt, beneath the pecto- 

 rals, or somewhat in advance of the latter. 



Three families compose this sub-order, two of which have furnished us with representatives 

 from the Pacific coast. The third, or that of Echeneidae, is, so far, unknown in that region. 



SvN. — T/ioradci, Linn. Syst. Nat. ed. X, 1758, 260.— Iconogr. Encycl. II, 1850, 204. 



Fishes with a thoracic position of the ventral fins are met with in some of the other orders 

 of the class, but that character is more subordinate yet, having not the value it is entitled to 

 amongst anacanthinians. 



Family GADIDAE, Bo nap. 



When told tliat tlie codfisli typifies this family it is enough to enlist the attention of our 

 readers. The cod-fisheries, and the immense trade connected with them, is one of the greatest 

 sources of wealth to a sea-coast population. 



Most of the representatives of this family, cod, haddock, frost fish, hake, coal fish, &c., are 

 tenants of the frigid and temperate waters, and generally of marine habits ; the ling or methy, 

 and allied species, being the only ones found in fresh waters. 



Their body is elongated, sub-fusiform in profile, either covered with small or moderate scales, 

 cycloid in structure, often hidden in the thickness of a soft skin. The head is proportionally 

 well developed ; the mouth large or moderate. Its upper surface generally scaleless ; sometimes 

 the cranial region is covered with minute scales. The teeth are varying between the rasp or 

 card-like type and the slender canines ; they are acerated, unequal in size, disposed upon 

 irregular series on both jaws, and the front of the vomer ; the palatine bones being toothless. 

 The j)rcnuixillar bones constitute almost exclusively the upper arcade of the mouth and bear 

 the teetli at the exclusion of the maxillaries, which appear towards the angle of the mouth 

 only. Tiie opercular apparatus is spineless. The gill apertures are wide, extending obliquely 

 forwards under the head, where they are continuous ; the branchial rays being six or seven ia 

 number on either side. 



