88 



PROF. P. M. DUNCAN ON THE OPHIURID^ 



arm. The tentacular openings are bounded, without, by a small, 

 short, and increasingly broad accessory plate. 



Arms short, with a leathery skin at the disk-notches, capable 

 of much horizontal motion, and broad and flat below, low at the 

 sides, and more or less angular above from the presence of the 

 nodular upper arm-plates. 



Colour in alcohol orange, with a little purple splashed on the 

 radial shields, nearly white below. 



A remarkable cribriform structure exists in many parts ; for 

 instance, on the bases of the boss-like nodules of the disk, on the 

 sides of the radial shields, on the flanks of the nodules between 

 the shields, on the sides of the large bosses at the margin, on the 

 upper flap of the side arm-plates, and on the upper arm-plate 

 except the boss. 



The jaw-frames are slightly cribriform, and so are the side 

 arm-plates, as seen from below, and here and there a few pores 

 occur on the lower arm-plates. The cribriform character is pro- 

 duced by a close, shallow, circular perforation, or rather pene- 

 tration, of the calcareous structures. 



Diameter of disk 18 millim. Length of arm 17*5 miilim., 

 breadth of arm outside the disk 3 millim. 



Locality. Elphinstone Island. 



Grenus Ophioglypha, Lyman. 

 Numerous young forms of indeterminable species. 

 Locality. Elphinstone Island. 



Grenus Ophioporagmus, Lyman. 



The next two forms to be considered have given some trouble 

 in regard to their classificatory position ; for whilst having the 

 general aspect and some of the characters of the genus Amphiura, 

 i here are some of the internal, as well as external, structures 

 present of the genus Ophiopliragmns, Lym. Some of the in- 

 ternal structures are, however, Ainphiuran, and are not seen 

 in the type of Ophiophragmus figured by Lyman, 'Challenger' 

 Report, Opbiuroidea, pi. xl. lig. 4. 



1. The junction of the mouth-frames, superiorly and at the 

 median line adorally to the first arm-bone, is stout and project- 

 ing. The upper brachial rims of the contiguous halves, to use 

 Lyman's words, "form an elevated crescent embracing the outer 

 end of the mouth-slit"; moreover, the interhraehial rims are in 



