22 SIX-GILLED SHARK. 



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 vcntrals 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 tuJpcs.) The lower lobe of this fin is falcate, and 

 grows more slender as it proceeds, being narrowest opposite 

 the notch. Along the posterior two 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. 



