70 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY II. 



bave in all cases been drawn witb considerable care and regard to 

 accuracy. 



The writer is nnder great obligations to Prof. Theodore Gill, of the 

 Smithsonian Institution, for aid of various kinds, both in his work 

 on the Siluridcc and in the prosecution of his ichthyological studies 

 generally. 



In the following descriptions, the "length of the body" is always 

 measured along the sides from the snout to the middle of the base of 

 the caudal fin. 



All of our species of fresh water Slluridce belong to the group called, 

 by Dr. Gill, in 18G2, Iotaluri. In 1864, Dr. Giinther recognized the 

 same group; but "to show his originality", as Prof. Agassiz used to say, 

 he, without assigned reason, changed the name to Amiurina. 



The following are the characters ascribed by Prof. Gill to the Ictahiri 

 (Report on Ichthyology. Captain Simpson's Explorations across the 

 Great Basin of Utah in 1859, p. 41G). 



Group ICHTH^LUEI. 



The body is more or less elongated, compressed posteriorly, and ter- 

 minating in a well developed caudal fin. The skin is naked and unpro- 

 vided with sucking cups. 



The head in profile presents the appearance of a more or less elon- 

 gated cone, and is covered with a skin which is generally quite thick. 

 It is more or less flattened, and broad above, and gradually becomes 

 narrowed to the convex snout. There is never a casque, or helmet. 

 The supraoccipital terminates in a point. 



There are eight barbels: the two maxillary, constant in the family; a 

 pair in front of the posterior nasal apertures; and two pairs arranged in 

 a curved line behind the lower jaw. 



The nostrils form nearly a transverse parallelogram between the in- 

 termaxillaries and the eyes; the anterior are suboval or subcircular, and 

 the posterior linear, with a raised margin, from the front of which the 

 upper barbels originate. 



The eyes are generally placed in the anterior half of the head. 



The branchial apertures are ample, continued from the supero-poste- 

 rior angles of the opercula to beneath the throat. 



The group of Ichthceluri consists of four genera : Ichthcclurus, Ami- 

 urus, Pelodichthys, and Noturiis. All the species known to be genuine 

 members of this group are North American, and all are included in the 



