5. SPINACIDJE, 
15 
teefli numerous, iu two or more series, the point so much turned aside 
that the inner margin forms a cutting edge, which is entire ; spiracles 
moderate ; no nictitating membrane ; gill-openings narrow ; fins all very 
small, the ventrals nearly opposite the second dorsal ; skin uniformly 
covered with minute tubercles. Species few, of the !Morthern Seas. 
(Latin, somniosiis, sleepy.) 
14. S. inici’OcepUalsis (Bloch) Gill. — Sleeper Shark ; Niase. 
Body robust, rapidly tapering behind; greatest depth about one- 
fifth the length; head somewhat less; mouth moderate, upper jaw with 
five rows of small shari) teeth, which are incurved and lancet-shaped ; 
loAver jaw with two rows of broad, quadrangular teeth, divided in their 
centres by a perpendicular ridge and directed outwards, about 2G teeth 
on each side; spiracles small; skin rough; fins small, the first dorsal 
about as large as the ventrals and larger than the second dorsal ; pecto- 
rals short ; caudal short and bluntish. L. 8 to 20 feet [Storer). Cape 
Cod to the Arctic Seas. 
(Squahts microccphalus Bloch, Schu. 135,* Sonmiosns hrevipinna Le SucTir, Journ. Ac. 
Nat. Sci. Phila. i, *222; Scymnus hrcvipimia Storer, Fish Mass. 235; Lcemaryus iorealis 
Giinther, viii, 426.) 
Family Y.— SPINACID^. 
{The Dog-fishes.) 
Body more or less elongate; head depressed; eyes lateral, without 
nictitating membrane ; mouth inferior, rather large, arched ; teeth com- 
pressed, variously formed ; nostrils inferior, lateral, near the front mar- 
gin of the snout ; spiracles moderate ; gill-ojtenings moderate, five on each 
side, all in front of the pectoral fins ; dorsal fins twoy each armed icith a 
spine ; the first dorsal in front of the pectorals ; anal fin wanting ; caudal 
fin with the lower lobe small or obsolete; ventral fins inserted pos- 
teriorly. 
Genera six or more ; species about fifteen; rather small sharks, chiefly 
of the Atlantic. {Spinacidw, part, Giinther, viii, 417-425.) 
* Teeth eqnal iu both jaws ; dorsal spines not concealed. 
a. Teeth very small, straight, pointed, each with one or two smaller cusps on each 
side Centroscyixium, 10. 
aa. Teeth moderate, simple, subqnadrate, each with a nearly horizontal cutting 
edge, and a point directed outward Squalus, 11. 
** Teeth unequal, those in the upper jaw erect, triangular, those in the lower jaw 
more or less oblique ; dorsal spines hidden beneath the skin. Centroscymnus, 12. 
