PISCES. 235 



and the lower part of Chesapeake Bay. They are called bow-fin 

 in Lake Champlain, dog-fish in Lake Erie, mud-fish in South Caro- 

 lina, &c. 



The next family, the Sauroidei, embraces but two genera, Lepidosteus 

 and Polypterus, both recent. The genus Lepidosteus is confined to North 

 America, where it is represented by about ten species peculiar to dilTerent 

 sections of country. There are two types of structure in Lepidosteus, one 

 with broad short jaws, the other with the jaws very narrow and elongated. 

 The dorsal is single, and placed far back opposite to the anal ; and the 

 whole appearance, a^ first sight, is not unlike a pike, for which reason one 

 species was called by Linnaeus Esox osseus, or bony pike. The air- 

 bladder presents a cellular character, somewhat like that of Amia. The 

 principal osteological features consist in the vomer being divided into two ; 

 an upper jaw composed of many pieces, a lower jaw similar in structure to 

 some Reptilia, as also in the vertebrae, one of whose' articulations is convex, 

 the other concave. There are two series of imbricated spines on the 

 anterior ray of each fin, the remaining rays being jointed. The scales are 

 combined into an impenetrable coat of mail, of almost adamantine 

 hardness ; and the jaws being provided with large conical teeth, with smaller 

 ones interspersed, and on the vomer, give the gar-fish, or gar-pike, a truly 

 formidable appearance. Gars attain a large size, especially the broad-billed 

 species, which has been known to measure ten feet in length. When of 

 proportions like this, it justly deserves the name of " Alligator Gar," fro*hi 

 the striking resemblance borne by the head to that of the alligator. It 

 would carry us too far out of our limits to extend these observations to the 

 remaining structural peculiarities of this highly remarkable and unique 

 genus, which ranges the waters of America, an isolated memorial of a past 

 generation. 



The genus Polypterus, by some justly made the type of a distinct family, 

 consists of four species, found only in the rivers of Africa. The most 

 striking external feature, by which it is distinguished from its nearest 

 ally, the preceding genus, is to be found in the great number of separate 

 finlets along the back, each consisting of a spine with some posterior rays. 

 The body is enveloped in mailed scales, of great hardness, as in Lepidosteus. 

 The upper jaw is undivided ; the lower, fish-like, not reptilian ; the vomer is 

 simple ; the vertebrae bi-concave ; and the fins without imbrications. 



The remaining families of the Holostean ganoids are all extinct ; and 

 we shall therefore confine ourselves to a brief synopsis only of their 

 characters. But few of the species, hitherto described, belong to North 

 America : these will be referred to in the {)roper place. 



The RosTRATi have a greatly elongated body, the head running out into 

 a narrow snout. The vertebral column is not much developed, only the 

 heaJ and the ribs being ossified. The dorsal and anal fins are of great 

 development. The scales are variable in shape and number. 



The Pycnodontes were fish of medium, or considerable size, with a short, 

 high, and much compressed body. The caudal fin alone is well developed ; 

 the dorsal and anal, which begin in the middle of the body and extend to 



489 



