SILUEID^. 
325 
and the ridges rounded ; supraoccipital slightly raised into a median 
prominence in its hinder half ; frontal vacuity not much elongated. 
Form. 4' Log. Lower Pliocene : Siwalik Hills, India. 
16402 h. Type specimen. 
Presented hy Col. Sir Prohy T. Cautley.^ K.G.B., 1842. 
Genus HETEROBRANCHUS, Geoffroy St. Hilaire. 
[Savigny, Descript. Egypte, vol. i. 1827, p. 305.] 
As Clarias^ hut hinder portion of dorsal fin adipose. 
Surviving in the freshwaters of Africa and the East Indian 
Archipelago. 
Heterobranchus palseindicus^ Lydekker. 
1886. Heterobranchus palceindicus, R. Lydekker, Palffiont. Indica, 
ser. X. vol. iii. p. 248, pi. xxxvi. fig. 4. 
Type. Nearly complete skull; British Museum. 
A species probably about 0'4 in length, known only by the skull, 
which is provisionally ascribed to Heterobranchus on account of 
its close resemblance to the skull of H. interynedius^ and also on 
account of the long backward extension of its supraoccipital bone. 
Not yet precisely definable, but differing from H. intermedins in its 
relatively shorter and wider frontal vacuity and its ethmoid much 
narrowed in front. 
Form. ^ Log. Lower Pliocene: Siwalik Hills, India. 
16402 c. Type specimen. 
Presented hy Col. Sir Prohy T. Cautley, K.C.B.^ 1842. 
Genus SILURUS^ Linnaeus. 
[Syst. Nat. ed. 10, 1758, p. 304.] 
Head not much depressed, the lateral muscles extending some¬ 
what forwards over the cranial roof, and the whole covered ^vith 
the soft skin. Gape of mouth extending to beneath the orbit; 
teeth very minute, villiform, present on the premaxillae and dentaries, 
also on the vomer but not on the palatines. Pectoral fin with 
robust spine, serrated on the posterior or both borders; pelvic fins 
with more than eight rays, arising behind the dorsal fin, which is 
short-based and without anterior spine; no adipose dorsal; anal fin 
much extended, almost or completely united with the caudal, which 
is rounded. Skin naked. 
The surviving species of this genus inhabit the freshwaters of 
the temperate parts of the Palsearctic Region, some extending even 
to the north of India. Eragmentary remains of a supposed extinct 
