CESTRACION TIBURO. IGl 



Zygnena tihuro Valenciennes, 1822, Mem. Mas. hist, nat., 9, p. 22G, pi. 12, f. 2'S2''; Yarrell, 1839, 



Brit, fishes, suppl., p. G4, f. 2; Gunth., 1870, Cat. fishes Brit, rnus., 8, p. 382; Dodeklein, 1881, 



Man. ittiol. Mcdit., 2, p. 50. 

 Plalysqualus tiburo Swain.s., 1839, Class., 2, p. 318. 

 Sphyrnias tiburo Gray, 1851. Chondroptorygii, p. 50. 

 Reniceps tiburo Gill, 18G1, Ann. N. Y. lye, 7, p. 412; Jordan & Gilbert, 1882, Bull. IG, U. S. nat. mus., 



p. 25. 

 Sphyrna (Reniceps) tiburo Jord. & Everm., 1896, Bull. 47, U. S. nat. mus., p. 44; 1900, ibid.. Atlas, pi. 5, 



f. 19. 



Front and sides of the head in continuous curves; front margin in the seg- 

 ment of a circle having its centre a short distance behind the symphysis of the 

 lower jaws. No indentation above the nostrils. Grooves from the inner edges 

 of the nostrils rudimentary. Nostrils separated from the eyes by one length of 

 the orbit. Hind margin of the oculonarial expansion short, about one fourth 

 as wide as the head. Mouth large, width about one third of that of the head, 

 or four fifths of the distance from the end of the snout, length nearly half of the 

 width. Teeth in fi rows, broad-based, oblique, notched on the outer border, 

 or indented on both edges in some; upper teeth with inner margins less concave 

 and with cusps less erect than the lower; median teeth small, more indented on 

 both edges; cusps smaller to obsolete toward the angles of the mouth. Pec- 

 torals broad, angles rounded. Origin of dorsal little behind the ends of the bases 

 of pectorals, length of base two thirds of the height, upper angle blunted, end 

 reaching a vertical from the ventrals. Origin of second dorsal little forward of 

 the middle of the anal base, end shghtly in front of that of the anal, outer angle 

 more produced and hind margin more concave than in that fin. Base of anal 

 longer than its distance from the caudal. Caudal less than one third of the 

 total, low^er lobe produced. 



Total length 22^, snout to abdominal pores 11, snout to fifth gill opening 5. 

 snout to mouth 2, greatest width of head 4|, snout to dorsal 7, and length of 

 caudal G| inches. 



Ashy brown, shading to white on the lower surfaces; fins darker with light 

 margins. Specimen described is from Massachusetts Bay. 



Tropical and temperate seas. 



