16 SELACHII : SQUALL — IV. 



7. SPHYRNA Rafinesque. (An old name from tri^vpa, 

 hammer.) 

 a. 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. zygaena (L.). Hammer-headed Shark. Width of 

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

 seas, N. to Cape Cod. (Eu^ (An old name from ^\iy6v, a cross- 

 beam.) 



bb. Head kidnej'-shaped, the frontal groove obsolete. (Renicept, 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.^. (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. 

 u. Koot of tail with a pit above ; caudal fin with two notches, 



Galeocehdo, 9. 

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



d. Teeth all serrate in the adult Caecharhinus, 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. GALEXJS (Rafinesque) Leach. (Mustelus Cuvier.) 



(yaXf(!f, shark; yaKerj, weasel.) 



o. Embryonotattached to uterus by a placenta; teeth very blunt. (Galeus.) 



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. (£«.) 



9. GALEOCERDO Muller & Henle. (yoKcos, shark ; 

 KfpSm, 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.) 



