312 CARTILAGINEI. RAIAD^. 



of the Sharks : the dorsals are two, sometimes 

 three in number, small, and placed very far back 

 upon the slender tail; sometimes, indeed, close to 

 its extremity ; a minute caudal is occasionally 

 seen, but more frequently wanting ; the dorsals 

 also are, in some species, obliterated. 



The eyes, and the temporal spiracles, are 

 placed on the upper surface : the latter are much 

 larger than in the Sharks, often exceeding the 

 size of the eyes ; they communicate internally 

 with the mouth and gills. The mouth, the 

 nostrils, and the gill-openings are placed on the 

 under- surface, and quite concealed from view in 

 the ordinary position of the fish as it flounders 

 along on the bottom of the sea. The gill-open- 

 ings agree with those of the Sharks in number, 

 form, and structure. The mouth is small, and 

 set with numerous teeth, which are arranged in 

 close array like paving- stones ; they are more or 

 less square, and flat ; but in old males, tke 

 middle ones assume a pointed form, overlapping 

 one another, and pointing backward towards tlie 

 throat. 



As in many of the Sharks, the eyes are fur- 

 nished with a nictitating membrane, or skin, which 

 can be drawn over the eye-ball at pleasure, 

 serving the purpose of an eyelid. 



The young of the Rays are enveloped at birth, 

 like those of some of the Sharks, in capsules of 

 thin horn or leathery substance. They are gene- 

 rally more square in form, with the angles pro- 

 duced, but not attenuated to long filaments. 

 The accompanying figure represents the egg- 

 capsule of the Common Skate, frequently found 

 on our sea-beaches, and commonly called Skate- 



