600 



PROCEEDINOS OF THE NATIONAL MUSEUM. 



VOL. 45. 



upper jaw; interorbital space convex, broad, 1.66 diameter of eye; 

 spiracle rather large, functional; snout semicircular in outline, the 

 preoral space greater than diameter of eye; nostrils large, with square 

 flaps; mouth large, its width twice eye, angular, the two sides form- 

 ing an angle of 45°; teeth small, similar in two jaws, about 28 in first 



Fig. 1.— Eridacnis radcliffki. Under side of head. 



row in each side of each jaw, pluricuspid, the central cusp rather 

 larger in upper jaw, with 2 or 3 proximal cusps and 1 distal cusp on 

 each tooth except 3 teeth nearest symphysis, which have a middle 

 cusp and 2 lateral cusps on each side; 3 teeth nearest symphysis in 

 lower jaw with middle cusp and 1 lateral cusp on each side, the num- 

 ber of cusps on proximal side increasing to 2, 3, and 4, while the 

 distal side has only 1 cusp ; gill apertures rather narrow, the last two 

 posterior to anterior margin of the pectoral, the fourth slit widest; 



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Fig. 2.— Eridacnis eadcliffei. Teeth of upper and lower jaws, greatly enlarged. 



dermal denticles with rounded base, a central sharp point, and a 

 short rectangular shoulder on each side, a central groove flanked by 

 lateral keels extending from base to sides of the pointed extremity, 

 and another groove on the outer side of each keel, the sides and base 

 of denticles having several rows of minute reticulations (not shown 

 in figure). 



