114 Bulletin 47, United States National Museum. 



OSTARIOPHYSI. 



This group, which includes the great majority of the living fresh-water 

 fishes of the world, is characterized chiefly by the modification of the 

 anterior vertebra?. These are coossified and have some of their lateral 

 and superior elements detached and modified to form a chain of small 

 bones, the Weberian ossicles, which, connect the air bladder with the ear. 

 The three orders, NEMATOGNATHI, PLECTOSPONDYLI, and SCYPHOPHORI 

 (Mormyridce), which compose this group, are doubtless derived from a 

 common stock, (bordptov, a little bone; (j>voo<;, bladder.) 



Order M. NEMATOGNATHI. 

 (THE CATFISHES.) 



Parietals and supraoccipital confluent. Four anterior vertebrae coossi- 

 fied, and with ossicula auditus or weberian apparatus. No .mesoptery- 

 gium. Basis cranii and pterotic bone simple ; no coronoid bone. Third 

 superior pharyngeal bone wanting, or small and resting on the fourth ; 

 second directed backwards. One or 2 pairs of basal branchihyals ; 2 pairs 

 of branchihyals. Suboperculum wanting, or modified into the uppermost 

 branchiostegal. Mesocoracoid present. Premaxillary forming border of 

 mouth above, except in one family, DIPLOMYSTID^E, in which the maxil- 

 laries also bear teeth. Interclavicles present. No scales. Skin naked or 

 with bony plates. 



"This division is the nearest ally to the sturgeons (CHONDROSTEI) among 

 Physostomous fishes, and I imagine that future discoveries will prove 

 that it has been derived from that division by descent. In the same way 

 the Isospondylous fishes are nearest the HALECOMORPHI, and have prob- 

 ably descended from some Crossopterygian, near the HAPLISTIA, through 

 that order. The affinity of the catfishes to the sturgeons is seen in the 

 absence of symplectic, the rudimental maxillary bone, and, as observed by 

 Parker, in the interclavicles. There is a superficial resemblance in the 

 dermal bones." (Cope, I. c., 454.) 



This group comprises the SILURID^E* and their relatives, now divided 

 into several families by Prof. Gill. (SiLURm^E, Giinther, Cat., v, 1-277.) 

 (v?jfj,a, thread ; yvados , jaw ; from the maxillary barbels, which are always 

 present.) 



ANALYSIS OF FAMILIES OF NEMATOGNATHI. 



a. Air bladder well developed, usually simple or with transverse constrictions, lying free in 

 the abdominal cavity. Mouth terminal; teeth villiform, conical, incisor or molar 

 like; intestines short; arranged in longitudinal folds; body naked, or with one series 

 of lateral plates; diaphragm membranous; tip of scapular process reaching basi- 

 occipital. Dorsal fin short, confined to the abdominal part of the vertebral column; 

 opercle well developed and movable; adipose fin normally present; gill openings gen- 

 erally wide; caudal vertebrae not compressed, the neural spines simple, spine-like. 

 Maxillary rudimentary, forming the base of a long barbel, the premaxillaries alone 

 forming the margin of the upper jaw. SILURIDJE, xxxiv. 



* In the arrangement of the tropical genera of NEMATOGNATHI, we have followed closely the 

 "Bevision of the South American NEMATOGNATHI," by Eigenmann & Eigenmann, 1890. 



