ICHTHYOLOGY. 



259 



of the suprascapula that the top of the coracoid is fixed. 

 Ill most osseous fishes tlie coracoid completes the lower key 

 of the scapular arch in joining its fellow by suture or syn- 

 chondrosis without the intervention of the radius ; but in 

 the Siluroids the radius descends to take part in this joint, 

 and sometimes even to occupy the half of the suture, 

 which is not unfrequently constructed of very deep inter- 

 locking serratures. The solidity of this base of the pectoral 

 spine is further augmented by the intimate union of the 

 radius and ulna, which often extends to junction by suture, 

 or even to coalescence ; and these bones, moreover, give 

 off two bony arches, — the first, a slender one arising from 

 the salient edge of the radius near tiie pectoral fin, and 

 going to the interior face of the ulna that is ajjplied to the 

 interior surface of the ascending branch of the coracoid ; 

 this process is analogous to one in the Ci/prmidre where it 

 is a separate bone : the second and broader supplementary 

 arcli does not exist in the Cyprinidce, and is often perfora- 

 ted by a large hole ; it also emanates from the same salient 

 edge of the radius, but proceeds in an opposite direction 

 to the inferior edge of the coracoid, a little before the in- 

 sertion of the pectoral spine. These two arches give at- 

 tachments to the muscles that move this spine ; in the 

 Synodontes and many Bagri, the upper arch remains in a 

 cartilaginous or ligamentous condition ; while in Malap- 

 terurus it is the lower arch that does not ossify, but both 

 are fully formed in the Siluri and many other Sihu'cids 

 more closely allied to that typical genus. The epicora- 

 coid is also wanting in the Siluroids (Nos. 49, 50, figs. 10 

 and 15.) The pterygoid and entopterygoid (25, 24, id.), 

 are reduced to a single bone, and so are the epitympanic 

 and pretympanic : the mesotympanic (31) is wholly wanting, 

 and the palatine is merely a slender cylindrical bone. The 

 suboperculum is likewise constantly absent in all the Silu- 

 roids. This long anatomical detail has been extracted from 

 the Histoire des Poissons, because without it descriptions 

 of this peculiar and interesting family could not have been 

 understood. 



The Siluroids have no true scales, though some of them 

 {Doras) have the lateral line armed with bony plates, and in 

 others {Calliclithys) these biserial plates are developed so as 

 to incase the entire body. There are also varieties of external 

 structure similar to those which occur in other large families 

 of fishes, such as the different positions of the fins, and even 

 the entire absence of certain of these members in some 

 groups. Many of the Siluroids are fresh-water fishes which 

 attain a great size, and they are what are called groinid 

 fishes, and remain habitually at the bottom of the pieces 

 of water that they inhabit. In the genus Silurus, as well 

 as in Pimelodus, the choroid vasoganglia and pseudo- 

 branchiae are both absent. Silurus glanis, L., is the largest 

 of European fresh-water fishes, and the only one of this 

 extensive genus inhabiting the ContineYit. It is smooth, 

 greenish black, spotted with black above, and yellowish- 

 white beneath. The head is large, with six barbels. It 

 sometimes attains the length of 12 or 15 feet, and the 

 weight of 300 or 400 lbs. As this creature is somewhat 

 unwieldy in its motions, it does not pursue its prey, which 

 consists of small fishes, but lies concealed among the mud, 

 and seizes such unwary stragglers as happen to come within 

 reach. The fishermen of the Spree say that they always 

 take the largest fish of this kind in a tlnmder-storm. In- 

 sects are the best bait for the younger ones. It has occa- 

 sionally been observed in the sea, but always near the 

 mouths of rivers. Gronovius and Temminck both authen- 

 ticate its occasional capture in the salt water. The flesii is 

 fat and sweet, and its lard has been employed in some ])laces 

 as a substitute for that of the hog. Sir Robert Sibbald, at 

 the conclusion of his list of river fishes, adds Silurus sire 

 Glanis ; from which it has been inferred that this gigantic 

 species may, at one period, have inhabited the Scottish 



rivers ; but this fish is a stranger to the waters of France, Classifica- 

 Spain, and Italy, as well as to England, which furnishes a t'on — Ma- 

 strong argument against the conclusion that has been drawn licopten. 

 from the sentence in Sibbald, unsiipported as it is by any ^^"V^"^ 

 reference to accounts of its capture in Scotland. In fact, 

 it is in the western European rivers that it is common, in 

 the Elbe to the north, and the Danube on the south, and 

 in the rivers still further west; and it is one of the fishes 

 brought to the market at Constantinople. It occurs in the 

 Scandinavian peninsula but rarely. In the rivers that tall 

 into the Caspian it is very common, but it is a stranger to 

 all the Siberian rivers which flow towards the Arctic Ocean. 

 It is undoubtedly the Glanis of Aristotle. 



The Synodonts of all the Siluroids that possess an adi- 

 pose fin are the most remarkable for the armature of the 

 head and nape, as they are also for their peculiar dentition. 

 They are either destitute of parietals, or these bones at an 

 early period of the life of the fish coalesce with the supra- 

 scapulae. The suprascapula; extend to the sides of the 

 supraoccipital, but this latter bone goes still further back- 

 wards to join the second interneural plate ; embracing, 

 in conjunction with it, the plate of the first interneural, as 

 we have mentioned above. The process of the suprasca- 

 pula which rests on the basioccipital descends lower, and 

 expands into a thin plate, to which the anterior lobe of the 

 air-bladder is attached. The ossicles of Weber are pre- 

 sent in their usual form ; but the first parapophysis of the 

 compound or coalescent anterior vertebral centra reaches 

 forward between the suprascapula and exoccipital, and 

 then sends a thin plate downwards into the air-bladder, in 

 which it forms a diaphragm. The coracoids and ulno- 

 radial bones, united below by suture, expand upwards in 

 form of a vertical plate, which constitutes a bony diaphragm, 

 dividing the branchial from the abdominal cavity, leaving 

 a single opening for the passage of the oesophagus. Some 

 species of Synodontis have been supposed to be the Nile 

 fishes mentioned by Strabo, under the name of xo'pos {por- 

 cus), which, according to Aristotle, are the only marine fish 

 that are not <ieterred by dread of the crocodile from as- 

 cending the Nile. This Saurian does not dare to attack 

 it on account of its strong spines. The Mugils also as- 

 cend the river, but it is under the protection of the Syno- 

 donts. The species of which Strabo speaks has not yet 

 been clearly made out, and may possibly be a Siluroid of 

 a different group. 



The Doras of South America have excited attention 

 by their habit of travelling during the dry season from 

 a piece of water about to dry up, in quest of a pond of 

 greater capacity. These jom-neys are occasionally of such 

 a length, that the fish spends whole nights on the way ; 

 and the bands of scaly travellers are sometimes so large, 

 that the Indians who happen to meet them fill many bas- 

 kets of the prey thus placed in their hands. The In- 

 dians suppose that the fish carry a supply of water with 

 them, but they have no special organs like the Ajiahas, slwA 

 can only do so by closing the gill-openings, or by retain- 

 ing a little water between the ])lates of their body, as Mr 

 Hancock supposes. This gentleman adds, that both the 

 Doras and CaUicldhys make regular nests, in which tliey 

 cover >ip their eggs with care, and defend them, male and 

 female uniting in this parental duty until the eggs are 

 hatched. The nest is constructed at the beginning of the 

 rainy season of leaves, and is sometimes placed in a hole 

 scooped out in the beach. The Calliclithi/s differ in many 

 |)arts of their skeleton from other Siluroids, and their cra- 

 nium does not owe its breadth to the expansion of the supra- 

 temporals, but to the development of the three frontals, and 

 the coalescence of a piece of the mastoid and suprascapula. 

 These fish, like the Doras, travel in search of water, and 

 sometimes bury themselves in the mud of wet meadows, 

 where they are often captured by the natives, who dig them 



