16 SELACHII : SQUALL IV. 



7. SPHYRNA Rafinesque. (An old name from 

 hammer.) 



. Teeth in both jaws oblique, each with a notch on the outside near the base ; 



no spiracles. 



b. Head truly hammer-shaped; a long groove extending forward from 

 nostrils. (Sphyrna.) 



9. S. zygsena (L.). HAMMER-HEADED SHARK. Width of 

 u hammer " twice its length. Gray. L. 15 to 20 feet. All warm 

 seas, N. to Cape Cod. (Eu.) (An old name from fryov, a cross- 

 beam.) 



bb. Head kidnej'-shaped, the frontal groove obsolete. (Reniceps, Gill.) 



10. S. tiburo (L.). BONNET-HEAD SHARK. Width of " ham- 

 mer " not nearly twice its length. Ashy gray. L. 3 to 5 feet. 

 Warm seas, N. to Va. (Eu.) (Tiburo, an Italian name of some 

 shark.) 



FAMILY VII. GALBORHINID^l. (THE TYPICAL SHARKS.) 



Sharks with two dorsals and an anal fin ; no spines ; tail mod- 

 erate, not lunate, bent upwards, the fin notched below near the 

 tip ; basal lobe short ; no caudal keel ; last gill opening above base 

 of pectoral ; eye with nictitating membrane ; head normally formed. 

 Genera 15, species about 60, found in all seas. 



a. Teeth blunt, paved, without cusps or cutting edges; spiracles present; 

 no pit at root of tail ; labial folds about mouth. . . . GALEUS, 8. 

 aa. Teeth more or less compressed, with sharp cutting edges. 

 b. Spiracles present ; teeth large; serrated. 



c. Root of tail with a pit above ; caudal fin with two notches. 



GALEOCERDO, 9. 

 bb. Spiracles none; teeth sharp; a pit at root of tail. 



d. Teeth all serrate in the adult CARCHARHINUS, 10. 



dd. Teeth all entire, all except the median ones oblique; their points 



turned away from the middle so that the inner margins are 

 nearly horizontal, and form a cutting edge. . SCOLIODON, 11. 



8. GALEUS (Rafinesque) Leach. (Mustelus Cuvier.) 



(yaXeos, shark; ya\er), weasel.) 

 a. Embryo not attached to uterus by a placenta ; teeth ver}^ blunt. ( Gahus.) 



11. G. canis (Mitchill). DOG SHARK. HOUND SHARK. BOCA 

 DULCE. First dorsal higher than long, its middle midway between 

 pectorals and ventrals; snout shortish. Pale gray. L. 3 feet. 

 Smallest of our sharks. N. Atl. ; common N. (Eu.) 



9. GALEOCERDO Muller & Henle. (yaAeo'j, shark ; 

 Kfp8o>, fox). 



12. G. maculatus (Ranzani). TIGER SHARK. Brown, with 

 numerous large dark spots. L. 10 feet. Warm seas ; rarely N. to 

 N. Y. (Lat., spotted.) 



