238 PISCES. 



the tympanal, jugal and temporal bones, and the preoperculum. 

 The hyoid bone is attached to the single pedicle just mentioned, and 

 supports branchiostegal rays, as in ordinary fishes, although they 

 are not so very visible, externally; it is followed by the branchial 

 arches, as usual, but neither of the three pieces compose the oper- 

 culum. These fishes have both pectorals and ventrals: the latter 

 are situated behind the abdomen. Their membranous labyrinth is 

 enclosed by the cartilaginous substance of the cranium; the sac, 

 which constitutes part of it, contains mere amylaceous masses, and 

 not stones. 



Sqtjalus, Lin. 

 Tlie Sharks form a first great genus distinguished by an elongated body, a 

 thick fleshy tail and moderate pectorals, so that the general figure ap- 

 proaches that of ordinary fishes; the branchial openings correspond with 

 the sides of the neck, and not with the under surface of the body, as we shall 

 see is the case with the Rays; the eyes also are on the sides of the head. 

 The snout is supported by three cartilaginous branches connected with the 

 anterior part of the cranium, and the rudiments of the maxillaries, inter- 

 maxillarles, and premandibularies are evident in the skeleton. 



Several are viviparous. The others produce ova invested with a yellow 

 and transparent horn, the angles of which are prolonged into horny cords. 

 The little branchial ribs are apparent, and there are also small ones along 

 the sides of the spine, which is completely divided into vertebrx. The ge- 

 nus is very numerous and authorizes various subdivisions. 



Cahchahias, Cuv. 



A numerous and by far the most celebrated tribe; with trenchant, pointed 

 teeth, most commonly dentated on the margin. The first dorsal is far be- 

 Fore the ventrals, and the second about opposite to the anal. The spiracles 

 are wanting; the nostrils are placed under the middle of the depressed snout, 

 and the last branchial apertures extend over the pectorals. 



Sq^ carcharias, L. (The White Shark.) This species attains the length 

 of twenty-five feet, and is recognized by its teeth, which in the upper jaw 

 nearly form isosceles triangles with rectilinear and dentated sides. The 

 lower ones consist-©f narrow points placed on wider bases, terrific weapons, 

 which are the dread of mariners. It would appear that it inhabits every 

 sea; but its name has frequently been applied to other species with tren- 

 chant teeth. 



Selache, Cuv., 

 In addition to the form of the Squali, and the spiracles of the Galei, is 

 furnished with branchial openings that are nearly large enough to encircle 

 the neck, and with small conical and unemarginate teeth. 



