Explanation of Plate IV. 



Fig. 1. Ophiopristis ensifera Ver. Dorsal side of a part of the disk 

 and the base of one arm. X 10. 



Fig. la. The same specimen. Oral side. X 10. 



Fig. \b. The same. Under side of portion of an arm, near the base, 

 with the spines removed; n. under arm-plate; /. side arm- 

 plate; 5. bases of spines; /. tentacle-scales. Much en- 

 larged. 



Fig. lr. The same. Side and profile view of one of the lower spines; 

 enlarged about 15 diameters. 



Fig. \d. The same spine; end view. 



