44 Bulletin ^7, United States National Museum. 



Characters of the genus included above. In the form of the head, there 

 is a perfect gradation among the species from the narrow hammer of S. 

 blochii, with the lobes 3 times as long as broad and deeply grooved 

 along the anterior edge, to the kidney-shaped head of S. tiburo, in which 

 the anterior grooves are obsolete. (cfyvpa, hammer.) 



a. Nostrils near the eyes. 



b. Nostril with the frontal groove short or obsolete; lateral extension of head niodt-ratc 



so that the head is rather kidney-shaped than hammer-shaped. 



c. RENICEPS, (rena, kidney ; ceps, head): Nostril with the groove obsolete ; anterior and 



lateral margins of head confluent into a semicircle. TIBURO, f>0. 



cc. PLATYSQTJALUS, (TrAarvs, broad; squalus): Nostril with a short groove; anterior margin 



of head curved, not continuous with lateral edges. TVDES, <il. 



SPHYRNA : 



bb. Nostril with a well-developed groove, which extends along the front of the hannni-r- 

 ehaped head, the anterior and posterior outlines of which are nearly parallel. 



ZYGJKNA, 02. 



Subgenus RENICEPS, Gill. 

 60. SPHYRNA TIBTJRO, (Linnrcus). 

 (SHOVEL-HEAD SHARK; BONNET-HEAD.) 



Body rather slender, not much compressed; head depressed, semicircu- 

 lar in front, reniforin, the posterior free margins short, the lateral margins 

 continuous with the anterior; pectorals large; first dorsal high, midway 

 between pectorals and ventrals; second dorsal much smaller, produced 

 behind, higher and shorter than anal; ventral fins moderate; caudal 

 moderate; mouth small, crescentic; teeth small, very oblique, with a 

 deep notch on the outer margin. Head 4 in length, 6 to tip of caudal; 

 width of head slightly less than length of head. Color uniform ashy, 

 paler beneath. L. 3 to 5 feet. Atlantic Ocean; abundant on our coast 

 from Longlsland southward; ranging to China, (tiburo, shark, in Spanish. ) 

 Squalits libiiro, LINNAEUS, x, 1758, 234, America. 

 Zygsena tiburo, GUNTHER, Cat., viu, 382,1870. 

 Reniceps tiburo, JORDAN & GILBERT, Synopsis, 25,1883. 



Subgenus PLATYSQUALUS, Swainson. 



61. SPHYRNA TUBES, (Cuvier). 



Intermediate in all respects between S. zygcena and S. tiburo, the head 

 longer and the hammer less produced laterally than in the former. An- 

 terior margin of the head much curved, but not continuous with the 

 lateral edge; length of hinder margin of one side of the hammer less than 

 its width near the eye. Nostril close to the eye, its groove longer than 

 in S. tiburo, but very short, continued for but a short distance along the 

 side of the head, and followed by a line of pores. A large shark, of the 

 warm seas; Gulf of California, West Indies, Mediterranean, and Indian 

 Ocean, (tudes, hammer.) (Eu.) 



Zygsena tudes (CuviER MS.), VALENCIENNES, Mem. Mus., ix, 225, 1822, Nice, after Pantouflier of 



Sphyrna tudes, MULLER & HENLE. Plagiostomen, 53, 1838. 

 Zygtena tudes, GUNTHER, Cat., vni, 382. 



Sphyrna tudes, JORDAN & GILBERT, Bull. U. S. Fish Com., 1882, 105. 

 Sphyrna tudes, JORDAN, Cat. Fish. N. A., 9, 1885. 



