196 THE PLAGIOSTOMIA. 



of the snout and the pectorals. Gill openings in front of the pectorals, width 

 about half the length of the orbit. Pectorals large, width less than length of 

 front margin, broader than long, outer angle rounded, hind margin concave, 

 inner angle somewhat narrowly rounded, fin applied to the flank subtending 

 the entire base of the first dorsal. Origin of the first dorsal above the axils of 

 the pectorals and spine above the middle of their inner free margin, middle of 

 the base above the inner angle of the pectoral, hind margin nearly straight, 

 upper angle rounded, hinder produced; spine strong, without grooves on the 

 sides, nearly two thirds as high as the fin; base of fin without the spine two thirds 

 of the height, nearly two fifths of the distance from the origins of the ventrals, 

 nearly one fifth of its distance from the second dorsal, or less than half the 

 distance from the last to the caudal. Base of second dorsal two thirds as long 

 as that of the first, more than one third of the distance from the caudal; spine 

 strong, nearly as high as the fin, inserted one length of the base without the spine 

 behind the ends of the ventrals, and nearly one length of the space between the 

 base of the second dorsal and the caudal behind the axils of the ventrals. Origins 

 of the ventrals much nearer those of the pectorals than to the origin of the 

 caudal, midway from that of the first dorsal to that of the second. Caudal as 

 long as the head, with a pit in front, subcaudal lobe produced, without a notch 

 between subcaudal and terminal, latter pointed with convex edges and blunted 

 end. Scales small, with a strong peduncle and a crown with three keels pro- 

 duced in sharp cusps the median of which is longest. A fold at each side of the 

 tail behind the second dorsal. Total length of a specimen from Juan Fernandez 

 36, snout to abdominal pores 19, snout to first dorsal lOi, snout to pectorals 8, 

 snout to mouth 3i, and caudal 8 inches. 



Back brown; whitish below; hind edges of lower fins and caudal lighter. 



Centrophorus. 



Squalus Rafinesque, 1810, Caratteri, p. 13. 



Centrophorus Muller & Henle, 1837, Sitzb. Akad. wiss. Berlin, p. 115; 1837, Wiegm. archiv, p. 398; 



1841, Plagios, p. 89. 

 Entoxychirus Gill, 1862, Proc. Acad. nat. sci. Phil., p. 498. 



Body fusiform, head depressed, snout blunt. Nostrils slightly oblique. 

 Eyes large, without a nictitating membrane; orbits long, with an angle at each 

 end. Mouth wide, little arched, with a deep groove and labial folds at each 

 angle. Teeth compressed, unUke in the two jaws; upper with triangular cusp, 

 more erect; lower with the inner or cutting edge directed outward. Spiracles 



