TEGUMENTARY SYSTEM. 183 



CLASS IV. PISCES.* 



TEGUMENTARY SYSTEM. 



THE skin and other tissues belonging to the tegumentary system 

 in the class of Fishes, exhibit very numerous diversities of structure ; 

 they have not, however, been so carefully investigated as hairs and 

 feathers. 



An Epidermis is always present, lubricated frequently by a copious 

 viscid secretion, and occasionally entirely devoid of scales, as in the 

 Cyclostomi, Lophius piscatorius, Muraenophis, and others, while, on 

 the other hand, many Fishes that appear almost smooth and scale- 

 less, such as the Burbot (Gadus Lota), are in reality provided with 

 small scales. The scales are usually disposed in an imbricated 

 manner upon the body of the Fish, and adhere by one extremity be- 

 ing implanted in a sacciform depression of the corium. 



The Scales generally exhibit great varieties of form, being either 

 round or angular in their contour, and frequently provided with 

 jagged edges. They usually consist of transparent, or highly re- 

 fractive laminae like mother-of-pearl ; upon their external surface 

 we observe a series of circular lines, which are disposed concen- 

 trically around a common nucleus or spot, which is not always 



Class PISCES. 



Sub-Class 1. Pisces Ossei s. Ostacanthi. 

 Order I. ACANTHOPTERYGII. Ex. Perch, Bream, Mackerel. 



II. MALACOPTERYGII. Ex. Carp, Pike, Salmon, Herring. 



III. PLECTOGNATHI. Ex. \ Diodon > Tetrodon, Orthagoriscus , Ostracion, Balis- 



ICSj oC. 



IV. LOPHOBRANCHII. Ex. Syngnathus, Hippocampus. 



Sub-class 2. Pisces Cartilaginosi s. Chondropterygii. 

 V. PLAGIOSTOMI. Ex. Rays and Sharks. . 

 VI. ELEUTHEROBRANCHI. Ex. Sturgeon, Chimara. 

 VII. CYCLOSTOMI. Ex. Petromyzon, Ammocates, Myxine, Bdellostoma. 



Sub-class 3. (Provisional) . Pisces Anomali. 

 VIII. AMPHIBIOIDEI. Ex. Lepidosiren. 

 IX. HELMINTHOIDEI Ex. Amphioxus, s. Branchiostoma. 



