103 NATURAL HISTORIC 



than, the others, and more or less ossified. The spines aie never found in the ventral fins, but 

 these fins are sometimes absent, and when present are placed in the abdominal region of the body. 

 When the air-bladder exists it is always connected with the throat by a pneumatic duct. 



This order of fishes includes, in Dr. Giinther's classification, twenty-nine families. It 

 comprises a vast multitude of genera, the Siluroid family alone including nearly 120 generic 

 types, while among the other families are such familiar fishes as the Eels, Conger Eels, Herrings, 

 Salmon, Pike, and Carp. 



FAMILY L SILURID^. 



The Siluroid fishes never have scales, and when the skin is not naked it bears on its surface 

 bony plates or scutes. The maxillary bones are here reduced to rudiments, and generally form 

 the support for a maxillary barbel, so that the margin of the upper jaw is formed by the 

 pre-maxillary bones only. The operculum is peculiar in wanting the sub-opercular bone. The 

 air-bladder communicates with the organ of hearing by means of auditory ossicles. The dorsal 

 and anal fins are variable in their development, and the characters from these organs, together with 

 the positions of the nostril and of the vent, are used to subdivide the family into great groups, 

 which Dr. Giinther names Homalopterse, Heteropterae, Anomalopterse, Proteropterse, Steiiobranchise, 

 Proteropodes, Opisthopterse, and Branchicolae. Each of these sub-families is again subdivided 

 according to the characters of the gill membranes, nostrils, lips, barbels, and positions of the fins. 



The Sihu'oid fishes ai-e found in the fresh waters of tropical and temperate regions, and the 

 few which enter the sea keep near to the coast. The genus Clarias has one group of species 

 confined to Africa and Syria, distinguished by having a prominent occipital crest which is 

 angular behind, while in East Indian species that prominence is less developed. The best- 

 known species is Clarias anguillaris, a fish eighteen inches long, from the Nile and West Africa. 

 Two species from the Ganges and East Indian Archipelago have the caudal fin united with 

 the dorsal and anal fins. As the waters dry up, these fishes make their way over the mud 

 by help of their fins in search of water, and at the time of these migrations are readily 

 captured. Heterobranchus is an allied genus distinguished by having two dorsal fins, the 

 anterior supported by rays, and the posterior fatty. Its distribution is chiefly African, but 

 one species Heterobranchus tapeinopterus has been found in Borneo and Banka. The number 

 of barbels in these fishes is usually eight two pairs on the mandibles, one pair of maxillary barbels, 

 and a nasal pair. The species of the genus Cnidoglanis are confined to the rivers and coasts of 

 Australia; in them the second dorsal fin is long, and is continuous with the caudal and anal 

 fins. In the genus Chaca there are no barbels on the nostrils, and the eyes are rudimentary. 

 'The species are East Indian. 



The only representative of the Siluroid family in Europe is the Silimis gianis, which 

 occurs in the rivers of Europe east of the Rhine. It is the largest of European fresh-water 

 fishes, and is said to have once been captured in a tributary of the Shannon. It is absent 

 from Britain, France, Spain, and Italy. It was formerly taken in Haarlem Meer, is rare 

 in Scandinavia, common in Prussia, Poland, Styria, the Danube, and the rivers of Southern 

 Russia. In the river Bug it has been taken sixteen feet long. Quoting from Valenciennes, 

 Yarrell states that a specimen captured near Thorn had the entire body of an infant in its 

 stomach ; and another example taken in Hungary is said to have contained the body of a woman 

 having a marriage ring on her finger and a purse full of money at her girdle. Young specimens 

 are valued for food, but are not easily captured. It is commonly found at the bottom, but rises 

 to the surface in stormy weather. 



The fat is iised in dressing leather, and the air-bladder is made into gelatine. There is 

 one small dorsal fin in this genus conspicuous for wanting the anterior spine. The anal fin, 

 however, is well developed, and extends back, so as to unite with the caudal fin, which is 

 rounded. 



The head and body are covered with soft skin, and the colour is a mottled brownish-olive. 

 The pectoral fin has a stout spine for its firsu ray, and this is slightly serrated at the free end. 

 The vent is placed behind the ventral fins. There are four barbels on the mandible, and one, 

 greatly elongated, is attached to each maxillary bone. 



