SIX-GILLED SHARK. 
22 
head wide and level over the summit, the breadth from eye 
to eye two inches and three quarters; the snout rounded in 
front and somewhat thick; eye large, staring, and slightly 
oval, without an angle on the anterior portion or inner canthus, 
and destitute of a nictitant membrane (a loose membrane, separate 
from the eyelids, and which covers a portion of the globe in 
some Sharks. It is a conspicuous organ in birds.) This portion 
of the eye is immediately over the symphysis of the lower jaw. 
The larger nostril is half way between the eye and snout, 
enclosed by a prominent margin, the orifice directed forward. 
Temporal orifice small, an inch and half from the posterior angle 
of the eye. The gape large, tongue bound down and not ap- 
parent; teeth in the upper jaw eight on each side, thin at 
the base, the points slender and sharp, not serrated, their 
direction towards the angle of the mouth. A small vacancy 
at the symphysis of this jaw, and a little in advance of this 
are four teeth, the two middle ones being parallel and very 
slender, the points directed towards the mouth; the other two 
more remote, and their points diverging. A little in advance 
of these are other two, which might easily escape observation, 
being slender, smaller, and more loosely attached. As in 
the upper jaw so in the lower there is a single row of teeth, 
but they differ greatly in form, being thin and broad, their 
anterior margin higher, the sloping edge finely serrated; they 
are six in number on each side of the symphysis, with what 
appears like a small bifid intermediate one. Orifices of the gills 
six, closely approaching each other; the openings long and 
encircling the throat. Pectoral fins wide, triangular. Body 
with the general proportions of the Picked Dogfish, but the 
head wider and larger. Dorsal fin single, its anterior edge 
fourteen inches from the snout, and opposite the space between 
the ventrals and anal— larger than the latter. Caudal fin six 
inches and a half long, and consequently more than one fourth 
of the length of the fish; and longer as well as more slender 
than that of any other British Shark except the Thrasher, — 
( Alopias mdp>es.) The lower lobe of this fin is falcate, and 
grows more slender as it proceeds, being narrowest opposite 
the notch. Along the posterior tw’o thirds of the upper margin 
of the tail is a row of spines, of three series, closely pressed 
together at the roots, and the two outmost regularly diverging. 
