556 Mr. C. T. Regan on the 



•was in most respects satisfactory. Several authors have 

 given family names to some of Giintlier's groups *, and of 

 these the Eigenmanns t have utilized differences in the 

 structure of the vertebral column and the air-bladder in 

 order to characterize the South-American families. Bou- 

 lenger J separated off as two families the Siluroids with all 

 the ribs sessile, retaining the remainder in one family, 

 SiluridsBj divided into eight subfamilies characterized by the 

 lengtli of the dorsal and anal tins, the freedom or union ■with 

 the isthmus of the gill-membranes, &c., the majority of these 

 groups being unnatural. 



Bridge and Haddon's § great memoir on the Siluroid air- 

 bladder is of considerable service in working out the classiri- 

 cation. Comparatively little has been written on the 

 osteology of the Siluroids, although Koschkaroffy has 

 recently given a useful account, with figures, of the skeletons 

 of several genera. The scheme here put forward is based on 

 the examination of a large series of skeletons, and a far 

 greater number of families is recognized and defined than in 

 any previous system. The majority of these are much 

 better characterized than most of the families of Percoids ; 

 the differences l)etween the Lutianidse and Scisenidse, for 

 example, are trifling compared with those between the Syno- 

 dontidse and Doradidse, which have usually been associated 

 in the same subfamily. 



In the following account I place first the Diplomystidae, 

 more generalized than any of the others in the normally 

 formed toothed maxillary and in the simple attachment of 

 the fifth vertebra to the complex. Next the Ariidae and 

 Doradidaj are considered, geneialized in form and in fin- 

 structure, but aberrant in the loss of the mesoeoracoid, and 

 they are followed by the Plotosidse and Siluridse, which 

 have a very long anal fin, but are primitive in some other 

 characters, such as the many-rayed pelvic fins. Then come 

 the Bagridte, widely distributed in Asia and Afi'ica, and they 

 are followed by the North-American Amiuridai and by a 

 number of Old- World families which may be regarded as 



* Gill (Smithson. Misc. Coll. xi. 1872) named, but deKned onlv by 

 references to Giinther's Catalogue, the families Ilypophthalmidit, '1 riclio- 

 niycteiid.e, Siluridie, Chacidae, Ploto-idie, ClariuUc, (jallicbthvidiv, Aijri- 

 id;e, Loricariida}, Sisoridte, and AsprediuidtB. 



t Occ. Papers Calif. Acad. i. (181)0). 



X Cambridge Nat. Hist. Fish. p. 58L> (1904). 



§ Phil. Trans, clxxxiv. (B) 1898, p. 65. 



|l liull. Soo. Nat. Moscow, PJOo, p. -'09. The genera described are 

 Loricaria, Synvdontis, Macrones or a related genus wrouglv named 

 Akysis, Clanas, Silui-us, Amis, Eutropius, Malopterurus. 



