SILUBID.E. 169 



and a little longer than that of the dorsal, denticulated on both 

 edges ; caudal forked. Colour brownish along the back, silvery 

 on the sides. 



Hob. Deccan, Poona, Tungabhadra and Kistna rivers. 



22. Genus AEIUS, Cuvier and Valenciennes. 



Syn. Sciades, sp., and Ariofos, Miill. & Trosch. ; ffe.vanemattchthys, 

 Guiritinga, Hemiarius, Cephalocassis, Netuma, and Paeudarius, Bleeker. 



Branchiostegals from five to six. Gill-inembranes not confluent 

 with the skin of the isthmus, and scarcely or not notched. Head 

 osseous superiorly, or covered with very thin skin. Eyes with free 

 orbital* margins. Mouth anterior ; upper jaw generally the longer. 

 Anterior and posterior nostrils placed close together, the latter 

 being provided with a valve. Barbels six one maxillary, and two 

 mandibular pairs. Teeth in the jaws villiform ; there are nearly 

 always palatine, and sometimes vomerine teeth, these may be villi- 

 forui or granular. First dorsal with one spine and seven rays ; 

 the adipose of moderate length or short ; pectoral spine strong and 

 serrated ; ventral fin with six rays, situated behind the vertical 

 from the posterior margin of the rayed dorsal fin ; caudal forked 

 or emarginate. An axillary pore. Air-bladder not enclosed in 

 bone. 



Considerable stress has been laid in this genus upon the charac- 

 ter of the teeth, and whether they are villiform or granular forms 

 a good method of division. Further subdivisions, dependent upon 

 the groups being continuous or not, appear unadvisable, because 

 in some species the size of the patches of palatine teeth increases 

 with age, thus altering their original conformation, and causing 

 one patch to impinge on its neighbour. 



There is likewise another question regarding the palatine teeth 

 in these fishes ; in Ariusjatius there are usually two small patches 

 of palatine teeth widely separated along the median line, but in 

 some specimens they are entirely absent as was stated by Hamilton 

 Buchanan, but subsequently denied by others. Consequently the 

 genus Hemipimelodus, Bleeker, has representatives in India, but 

 they are abnormal specimens in which either the palatine teeth 

 were absent from birth, or else have become lost through age. Such 

 species would appear to be amongst those having globular teeth. 



The air-bladder is not enclosed in bone, is large, heart-shaped, 

 and internally subdivided into five chambers, which communicate 

 together anteriorly : the front one, which is the largest, occupies the 

 anterior portion ; behind this a median septum divides the bladder 

 down the centre, and lateral partitions subdivide the posterior 

 chambers into four. (See A. gayora, p. 185.) 



The breeding of these fishes is peculiar and deserves attention. 

 The eggs of Arius are largo, averaging about 0'5 to 0-6 of an inch 

 in diameter, and I have found many males of the genus, and also 



