92 



PROF. P. M. DUNCAN ON THE OPHIURIDiE 



separating the lower arm-plates there ; meeting on the upper 

 surface of the arm close to the disk by a narrow surface. The 

 spines are on the exposed narrow edge of the plate, and are 

 three in number except close to the disk, where there is a fourth. 

 They are subequal, short, stout, cylindro-conical, striated, sharp, 

 and glassy ; their length is not equal to that of bhe widtli of the 

 upper arm-plate. The tentacle-scale is small and spinulose. 

 Tentacles long and stout. The colour of the animal is either light, 

 brown or white. 



With regard to the internal construction of the skeleton, it 

 appears that the form of the upper part of the arm -bones 

 resembles that seen in Amphiura, but there is an approach to the 

 peculiar structure of the genus OpMophragmus in the crescentic 

 junction of the mouth-frames at the mouth-slits ; moreoveT, the 

 interbrachial rims of the frames project and are not widely sepa- 

 rated. There is no peristomial plate. The position assumed in 

 the specimens by the genital plates and scales is very remarkable) 

 but it may be due to post-mortem causes. The oral ends of the 

 plates and scales, instead of being parallel with the side of the 

 arm in continuation with the general direction of the rest 

 of the structure, are in contact with the side arm-plates 

 immediately below the position of the aboral ends of the radial 

 shields. The plates and scales are thus nearly vertical and the end 

 of a radial shield is forced up to a much higher level than the top 

 of the arm, and of course there is a considerable space between 

 the upper surface of the arms and the underpart of the disk. 



Locality. King Island. 



Genus Ophiocnida, Lyman. 



Ophiocntda sexradia, sp. nov. (Plate VIII. figs. 10, 11.) 



Disk small, tumid above and at the margin, irregularly hexa- 

 gonal, covered with a thick skin with numerous close, short, 

 thorned stumps. 



No scales or radial shields are visible. A skin with a very 

 delicate, small, overlapping scaling is in the interbrachial spaces 

 below, and there are some stumps on it near the margin. Two 

 large generative slits, which come as far inwards as the aboral 

 process ( genital scales) of the mouth-shield. Mouth-shields small, 

 about a.- long as broad, lozenge-shaped with the .-ingles rounded. 

 Side mouth-shields small, short orally, and largest near the arms, 

 usually not meeting orally, and touching the first and second 



