96 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 



way the lMpondylous fishes are nearest the Halccomorplu, and have 

 probably descended from some Crossopterygian, near the Haplistia, 

 through that order. The ailiuity of the cat-fishes to the sturgeons is 

 ii in the absence of symplectic, the rudimental maxillary bone, and, 

 tua i.l served by Parker, in the interclavicles. There is a superficial 

 resemblance in the dermal bones." (Cope. 1. c., 454.) 



This group comprises the Siluridcc and their relatives, now divided 

 into several families by Professor Gill. ( ^<i. a, thread ; pd0?, jaw; from 

 the maxillary barbels, -which are always present.) 



ANALYSIS OF THE FAMILIES OF NEMATOGNATHI. 



'OpiTculuin present: dorsal fin, if present, short, anteriorly placed. . . SiLunnxdE, 29. 



FAMILY XXIX. SILURID.E. 

 (The Cat-fishes.) 



I5ody more or less elongate, naked or covered with bony plates. 

 No true scales. Anterior part of head with two or more barbels, the 

 base of the longest pair formed by the rudimentary maxillary. Margin 

 of upper jaw formed by premaxillaries only. Suboperculum absent; 

 operculmn present. Dorsal fin usually present, short, above or in front 

 of the vent nils. An adipose fin usually present. Anterior rays of dor- 

 sal and pectorals usually spinous. Air-bladder usually present, large, 

 and connected with tte organ of hearing by means of the auditory ossi- 

 de<. Lower pharyngeals separate. 



After the removal of numerous aberrant forms as distinct families, 

 the family of S'llnritltv, as understood by Professor Gill, contains more 

 than loo genera and upward of 900 species. Most of the SiUtriflcc are 

 fie-h -water iKhes, inhabiting the rivers of warm regions, particularly 

 South America ami Africa. Comparatively few of them are marine, and 

 the<e few are mostly tropical. 



( )ur species all belong to the division called by Dr. Giiuther, Siluridcc 

 r,;>trr<>i>t< r<r. and thus characterized: 



"The ra\ed dorsal is always present, short, with not more than 12 

 soft i;i\ 9, ami belongs to the abdominal portion of the vertebral column, 

 being placed in advance of (lie ventrals. The adipose fin is always 

 present and well developed, although frequently short. The extent of 

 the anal is much infwriur to that of the caudal vertebral column. The 

 gill niembi.ine> are not continent with the skin of the isthmus, their 



