SQUALID^E. IV. 15 



ee. Last gill opening before base of pectoral ; dorsal fins subequal. 



CARCHAKIID^E, 9. 

 dd. Caudal fin lunate, the lower lobe not much shorter than the upper ; 



tail with a keel on each side, last gill opening before pectorals. 

 h. Gill openings rather large; teeth large ..... LAMNID^E, 10. 

 hh. Gill openings very large, nearly meeting both above and below; 

 teeth small (largest of all fishes) ..... CETORHINID^E, 11. 

 art. Pectoral fins very large, wing-like, expanded at the base in front, this ex- 

 pansion being separated from the neck by a deep notch; no anal fin. 



SQUATIKID^E, 12. 



FAMILY IV. SQUALID^EJ. (THE DOG-FISHES.) 



Sharks with two dorsal tins, each armed with a stout spine, and 

 without anal fin ; no nictitating membrane ; spiracles moderate ; 

 gill openings narrow, all before pectorals ; ventral fins inserted 

 posteriorly ; teeth small, compressed ; nostrils inferior, near front 

 of snout. Genera 6 ; species about 15; small sharks, chiefly of the 

 Atlantic. (Spinacidce Auct.) 



a. Teeth in both jaws, simple, subquadrate, each with a nearly horizontal 

 cutting edge, and a point directed outward; dorsal spines strong. 



SQUALUS, 5. 



5. SQUALUS (Artedi) Linnaeus. 



7. S. acanthias L. DOG-FISH. Dorsal spines not grooved; 

 slate-color, back with whitish spots fading with age. L. 3 feet. 

 North Atl., S. to Cuba; abundant N., its liver valued for the 

 "Dog-fish oil." (Eu.) (Gr. anavQias, having spines.) 



FAMILJ V. SOMNIOSID^]. (THE SLEEPER SHARKS.) 



Sharks with two dorsal fins, both without spine, and no anal fin, 

 the first dorsal much before ventrals, otherwise essentially as in 

 the Squalidce. Genera 5 ; species 5 or 6, mostly large sharks of 

 the Atlantic. 



a. Dorsal fins about equal; upper teeth lancet-shaped, incurved; lower quad- 

 rate with a horizontal edge, ending in a point directed outwards; fins 

 very small ................ SOMNIOSUS, 6. 



6. SOMNIOSUS Le Sueur. (Lat., sleepy.) 



8. S. microcephalus (Bloch). SLEEPER. NURSE. Color 

 blackish ; caudal blunt. L. 10 to 18 feet. Arctic seas, S. to Cape 

 Cod. (Eu.} (pi/epos, small ; KftyaXfj, head.) 



FAMILY VI. SPHYRNIDJE. (THE HAMMER-HEADED 

 SHARKS.) 



Characters of the Galeorhinidce, except that the head has a form 

 hammer-shaped or kidney-shaped, its sides being much extended, 

 the eyes borne at the ends of the hammer. One genus, with 4 or 

 5 species ; large sharks of the warm seas. 



