70 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY—II. 
have in all cases been drawn with considerable. care and regard to 
accuracy. ; 
The writer is under great obligations to Prof. Theodore Gill, of the 
Smithsonian Institution, for aid of various kinds, both in his work 
on the Siluride and in the prosecution of his ichthyological studies 
generally. 
In the following descriptions, the “length of the body” is aiways 
measured along the sides from the snout to the middle of the base of 
the caudal fin. 
All of our species of fresh water Siluride belong to the group ealled, 
by Dr. Gill, in 1862, IcTALURI. 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 Ictaluri 
(Report on Ichthyology, Captain Simpson’s Explorations across the 
Great Basin of Utah in 1859, p. 416). 
Group iCHTHAILURI. 
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 subcireular, 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 Jchtheluri consists of four genera: Ichthelurus, Ani- 
urus, Pelodichthys, and Noturus. All the species known to be genuine 
members of this group are North American, and all are included in the 
