CATALOGUE OF YERTEBEATES. 663 



ISURUS, Raf. 

 (Oxyrhina. Isuropsis.) 

 I. dekayi, Gill, (punctata, De K., glaucus.) Mackerel Shark. Porbeagle. 

 Snout long and pointed ; teeth long, lanceolate, with entire 

 edges without basal cusps ; first dorsal inserted well behind the 

 pectorals; dark bluish gray above, white below; middle teeth 

 longest. Length, 10 feet. /. gtaucua is the Asiatic species, with 

 shorter pectorals. 



" This large species is not unfrequently seen and taken along 

 our coast. It chases the schools of mackerel generally, and is 

 seen on our coast frequently or not, as the latter fish are abun- 

 dant or otherwise." 



Family CETORHINID^. 



Bashing Sharks. 



Very large, with wide gill openings that reach nearly to middle of 

 throat; teeth small and conical; spiracles small, above corners of 

 mouth ; first dorsal large and midway between the large pectorals and 

 the ventrals. 



OBTORHINUS, Blainv. 



(Squalus. Selachus.) 



C. maximuB, Gunner. Basking Shark. 



Skin very rough ; head and eyes small ; nose blunt ; teeth in 

 six or more rows of two hundred in each row ; largest of sharks. 

 Length, 40 feet at times. 



"Occasionally, in August and September, a specimen of this 

 species is seen, but they are seldom captured. They are a north- 

 ern species that are seen on our coast only as stragglers." 



Order RAI>E. 



(RAJIDES. BATOIDEI.) 



Five pairs of gill openings on the lower surface ; no anal fin ; dor- 

 sal fin on tail ; body flat, formed laterally of the expanded pectorals ; 

 tail slender, with small fin. 



