OSTARIOPHYSI 589 



(vil) HYPOPHTHALMINAE. Dorsal fin short, behind the ven- 

 trals, anal long ; gill-clefts wide or interrupted below. South 

 American : Ageniosus, Trachelyoptervs, Auchenipteriis, Epapterus ) 

 Tetranematiclitliys, Hypophthalmus, Hclogenes. 



(viii.) TRICHOMYCTERIXAE. Dorsal fin short, far back, behind 

 the ventrals ; no adipose fin ; anal short ; operculum and inter- 

 operculum armed with erectile spines. South American : 

 Tricliomycterus, Eremopliilus, Stegophilus, Vandellia, Acan- 

 thopoma. 



Our knowledge of the distribution in time of the Silurids 

 is still very scanty, and throws no light on the derivation of 

 the group. Arius, and two genera apparently related to 

 it, Rldneaster and Ui/rkhatfUitm, have left remains in the 

 Eocene of Europe and North America, and traces of various 

 recent genera have been found in later Tertiary deposits 

 in Europe, Asia, and North and South America. 



The habits of the Silurids are extremely diversified, and 

 the shape of the body varies accordingly. The body may be 

 very short and the head enormous and excessively depressed, 

 for instance in the Indo-Burmese Chaca lophioides, which, as its 

 name implies, resembles the Fishing-Frog or Angler; stout and 

 Cotiua-]Ss& in some South American Pimelodus] Loach -like 

 in Trichomycterus and Stegophilus ; more or less Eel-shaped in 

 Clarias and its allies, etc. ; the extreme of slenderness obtains in 

 the African Channalabes, the body being excessively elongate 

 (over 100 vertebrae), the ventral fins absent, and the pectorals 

 rudimentary or absent. Among other remarkable forms may 

 be mentioned the Indian Sisor, which resembles Aspredo, and in 

 which the upper caudal ray is much thickened and greatly 

 prolonged ; Pseudecheneis, living in rapids of the Himalayas and 

 Khasia hills, provided with a transversely plaited ventral disk 

 between the pectoral fins ; the African Phractura and Ander- 

 sonia, resembling Loricaria; and the likewise African Belonoglanis, 

 comparable to a Needle-Fish. The spines which so frequently 

 arm the dorsal and pectoral fins may be barbed or serrated, 

 and constitute formidable defensive weapons ; in the South 

 American Ageniosus valenciennesi, the maxillary bone is trans- 

 formed into a strong, barbed, erectile spine, replacing the 

 barbel. Stings of even the smaller Cat -Fish are at least 

 as painful as that of a bee, and this is probably due to some 



