SHARKS AND RAYS OF BEAUFORT, NORTH CAROLINA. 



265 



third of anal, distal margin slightly concave, lower lobe acuminate, reaching nearly to base of caudal; 

 pectorals small, distal margin nearly straight; ventrals broad, distal margin very slightly concave; anal 

 larger than second dorsal, anterior lobe recurved, acute-angled, distal margin deeply concave, posterior 

 lobe acuminate, not as long as that of second dorsal. 



Color. — Dorsal surface deep olive-gray, sides light olive-gray, shading into white of belly; fins body 

 color, with dusky margins. 



Stomach contents. — Three menhaden 21, 22.2, and 22.8 cm. long respectively. One taken in 1913 

 had been feeding on small shrimp. A male 132 cm. long taken in Newport River, August 3, 1914, had 

 in its stomach foiu- menhaden, each 26 cm. long. 



This species is not common in the harbor. None was taken by the laboratory force in 1912, only 

 one in 1913, and two in 1914. The best places to seine for them are near the mouthsof the rivers flowing 

 into the harbor. According to Coles this is one of the most abundant sharks in the Cape Lookout region 

 during the summer months. On one occasion he captined 65 specimens, averaging about 4 feet in 

 length, at a single haul of the seine. 



17. Cestracion tiburo (Linnaeus). Bonnet -nosed shark; shovel-headed shark. 



Reniceps iiburo. Yarrow, 1877, p. 217: Jordan and Gilbert, 1879. p. 387. 



Sphyrna tiburo, Jordan. 1SS6. p. 26: Jenkins. 1887, p. 84; Wilson. 1900. p. 355; Smith, 1907. p. 35, fig. 5: Gudger. 1907, p. 1005; 

 id., 191S, p. 143; Coles, 1914, p. 90. 



Teeth.— Teeih. in 



29-32 



_— rows, with a like variation in form as described for C. zygip.na, but possessing 



no diagnostic differences by which they may be distinguished from that species. 



In a female 124 cm. long, there are no marked differences from the male of C. zygcena, 132 cm. in 

 length; a female 94 cm. long has the same type of teeth but has only two rows of cuspless teeth at angles 



Denticles, Cestracion tiburo, 89.8 cm. long, from Beaufort, N. C. 



in upper jaw and four in the lower. A female 147.5 '^™- '°iiS ^^ '^'^ long, pointed cusps, oblique in 

 upper jaw, erect in the lower and compressed teeth, like those of the male of zygmna, 124.5 '^™- long. 



The average number of rows of teeth is lower in tiburo than in zygcena. The differences in the form 

 of the teeth are not sexual. The jaws of those specimens in which tlie teeth are compressed, with oblique 

 cusps in tlie upper jaw and erect or suberect in the lower are markedly smaller in proportion to the 

 size of the fish than those with the pavement type in each species. As the specimens were not compared 

 nor saved it is not known whether differences other tlian those of the teeth existed. 



Denticles. — The dermal denticles are larger and not so closely imbricated, but quite similar in 

 sculpturing to examples of C. zygeena, of the same size. In an example 89.8 cm. long they are about 

 0.27 mm. long by 0.3 mm. broad, imbricated, five-keeled, keels parallel; apical margin five-lobed, lobes 

 acute-angled, pedicels slender, resting on a small rhomoidal basal plate. 



