SHARKS AND RAYS OF BEAUFORT, NORTH CAROWNA. 247 



Family ISURID^. The mackerel sharks. 



KEY TO THE GENERA. 



a. Gills without strainers; teeth compressed; one or two series functioning. 



h. Teeth large, triangular, edges serrated, bcisal denticles absent Carcharodon. 



bb. Teeth awl-shaped, smooth-edged, with or without basal denticles hums. 



nil. Gills with strainers; teeth small, conical, several series functioning Cetorhinus. 



Genus CARCHARODON Smith in Muller and Henle. 

 3. Carcharodon carcharias (Linnaeus). 



Carcharodon carcharias. Coles. 1914. p. 91. 



26 

 Teeth. — Teeth in — rows, large, erect, triangular, coarsely serrated, cutting edges nearly straight; 



teeth relatively longer and narrower, without distinct basal shoulders and more uniform in size than 

 in species of Carcharhinus; third row on each side of symphysis of upper jaw of slightly smaller teeth 

 than those in the second or fourth rows; teeth in lower jaw similar in form to those in the upper except 

 that they are narrower, edges slightly more concave; a wide toothless space at symphysis of lower jaw; 



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Fig. .1. — Teeth, Carcharodon carcharias, from Woods Hole, Mass. (U. S. National Museum no. 11845.) — 'r C/ O y ^0^''*xy C*^ 



two rows of small teeth at angles of mouth. (Description of teeth based on a set of jaws in tlie United 

 States National Museum, from Woods Hole, Mass.) 



Dermal denticles. — As figured by Garman (The Plagiostomia, pi. 5, fig. 9), the denticles are regular 

 in arrangement, slightly overlapping, three-keeled, keels parallel; lateral keels submarginal; apical 

 margin with three sharp-pointed lobes, median one most prominent; basal margin rotmded; pedicel 

 and base small. 



In 1905 and again in 1913 Coles observed several very- large sharks in the vicinity of Cape Lookout 

 which he believed to be this species. As yet none has been captured on the coast of North Carolina. 



Genus ISURUS Raflnesque. Mackerel sharks. 

 4. Isurus tigris (Atwood). 



Isuropsis dekayi. Yarrow, 1877, p. 217. 

 Isurus dekayi. 1907, p. 31. 



Teeth. — "Teeth smaller than those of /. oxyrhynchus , similarly without basal denticles, with a sharp; 

 slender ciu-ved cusp, and with the third tooth at each side of the middle of the mouth on the upper 

 jaws much smaller than the second or the fourth."" 



Denticles. — No material or description available. Dr. Yarrow states that he saw a skeleton of 

 this species. Although later observers have failed to find examples of it and have not included it in 

 their faunal lists, the species doubtless visits these waters. 



a Garman. The Plagiostomia. p. 37. 



