CAT-FISHES. 559 



have to be mentioned : Soleotalpa and Apionichthys, Soles 

 ■with rudimentary eyes ; Amviopleurops, Aphoristia, and 

 Plagusia, which are closely allied to Cynoglossus, the latter 

 genus having the lips provided with tentacles. 



FOURTH ORDER— PHYSOSTOMI. 



All the fin-rays articulated, only tlu first of the dorsal and 

 pectoral fins is sometimes ossified. Ventral fins, if present, 

 abdominal, luithout spine. Air-bladder, if present, with a pneu- 

 matic duct (except in Sconibresocidm). 



FiEST Family — Silueid^. 



Shin naked or with osseous scutes, hut without scales. 

 Barbels always present ; maxillary hone rudimentary, almost 

 always forming a support to a maxillary barbel. Margin of 

 the upper jaw formed by the intermaxillaries only. Suboper- 

 culum absent. Air-bladder generally present, comm-uniqccting 

 with the organ of hearing by means of the auditory ossicles. 

 Adipose fin present or absent. 



A large family, represented by numerous genera, which 

 exhibit a great variety of form and structure of the fins ; they 

 inhabit the fresh waters of all the temperate and tropical 

 regions ; a few enter the sea but keep near the coast. The 

 first appearance of Siluroids is indicated by some fossil remains 

 in tertiary deposits of the highlands of Padang in Sumatra, 

 where Pseudeutropius and Bagarius, types well represented in 

 the living Indian fauna, have been found. Also in North 

 America spines referable to Cat-fishes have been found in 

 tertiary formations. 



The skeleton of the typical Siluroids shows many peculia- 

 rities. The cranial cavity is not membranous on the sides, 



