XX1 OSTARIOPHYSI 589 
(vu.) HyPporpHTHALMINAE.—Dorsal fin short, behind the ven- 
trals, anal long; gill-clefts wide or interrupted below. South 
American: Ageniosus, Trachelyopterus, Auchenipterus, Epapterus, 
Tetranematichthys, Hypophthalmus, Helogenes. 
(vul.) TRICHOMYCTERINAE.— Dorsal fin short, far back, behind 
the ventrals ; no adipose fin; anal short; operculum and _ inter- 
operculum armed with erectile spines. South American: 
Trichomycterus, Eremophilus, 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, Rhineaster and Puchlandiwm, have left remains in the 
Kocene 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 
Cottus-like in some South American Pimelodus; Loach-lke 
in Trichomycterus and Stegophilus; more or less EKel-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 
