216 ZOOLOGY. 



cataractus, or the ii\\\ fish of Pennsylvania, attains to a considerable size, 

 perhaps larger than that of any other alHed form in this country ; specimens 

 have been seen nearly tv\^o feet in length, and weighing several pounds. 

 This size is, however, exceeded by many of the European species. The 

 peculiar genus Exoglossum is characterized by a trilobed lower jaw, the 

 middle lobe I'ormed by the extremity of the lower jaw, the lateral by cartila- 

 ginous expansions. Another interesting sub-family, embracing several 

 genera and inany species, is that of the Suckers, or Catastomi, known by 

 the highly fleshy lips, which can be applied to any object like a sucker. 

 The pharyngeal teeth are columnar or prismatic, not hooked and truncated. 

 They are found abundantly throughout North America ; and different species 

 are known by the various names of carp, sucker, mullet, buffalo-fish, red- 

 horse, ifec. PL 81, figs. G, 7, represent Cobitis fossilis and E. harhatula, 

 European species of a form not found in North America. 



The concluding family of the order Malacopteri, or Physostomi, is found 

 in the Silurid.e, represented in North America by the catfish. Fishes of 

 this family have the skin either naked, and covered with a slimy secretion, 

 or provided with osseous plates of various number and shape. The head 

 is usually depressed, and provided with a variable number of barbels. In 

 most, there is a second and adipose dorsal, sometimes confluent with the 

 caudal. The first rays of the dorsal and pectoral fins are generally enlarged 

 into strong spines ; and the pectoral spine is capable of being inflexibly 

 fixed, by peculiar mechanism, in a direction perpendicular to the axis of 

 the body. The edge of the mouth is formed by the intermaxillaries sus- 

 pended from the sides of the ethmoid, which enters into the outline of the 

 mouth, forming the superior median portion. The sub-operculum is absent 

 in the whole family. 



Species of this polymorphous family are found distributed throughout the 



globe. In Europe, however, there is found but one species, the Sihirus 



glanis, or sheat fish. This species, interesting from the fact of its being the 



largest fresh-water fish in Europe, the sturgeons excepted, is most abundant 



in central Europe, its existence in England being hypothetical. The weight 



has been known to exceed lOOlbs., in this respect equalling some of the 



American Silurida;. It diflfers from the North American species in the 



absence of a posterior adipose dorsal, in the very small true dorsal, and 



in the very long anal. Other species of this restricted genus, Sihirus, are 



found in various parts of Asia, and perhaps Africa, but not in America. 



The American forms are highly varied, those of the northern continent, 



however, being quite uniform in structure. The two most conspicuous 



fresh-water genera are Pimelodus and Noturus ; the former with a distinct 



adipose dorsal, the latter with this dorsal confluent with the caudal, 



Nvmierous species of Pimelodus (cat-fish, horned-pout, bull-head) occur 



in the various waters of North America, some of which acquire a large 



size. One species, from the Mississippi, has been known to weigh over 



lOOibs. The flesh of many species is highly prized, owing to its sweetness 



and freedom from bones. The genus Noturus, known provincially as stone 



cat-fish, embraces but few species, found in the Atlantic streams south of 



420 



