242 THE VOYAGE OF H.M.S. CHALLENGER. 



marginal plates, the whole forming a uniform covering which prevents the possibility of 

 distinguishing the individual plates on superficial examination. Some of these papillae 

 appear to simulate incipient pedicellariag, but their character is not well defined. 



The madreporiform body is small and oval, situated a little on the outer side of a point 

 midway between the margin and the centre of the disk ; and its surface is grooved with 

 comparatively few, narrow, highly convoluted, and irregular striation furrows, wide apart, 

 causing it to have a rather coarse appearance. 



Colour in alcohol, a bleached yeilowish grey ; sometimes with traces of a dark brown 

 or faded purple shade on parts of the paxillar area, which lead to the inference that that 

 might probably have been the original colour. 



Locality. — Station 311. Off the western coast of South America, near the entrance to 

 the Strait of Magellan, opposite Port Churruca. January 11, 1876. Lat. 52° 45' 30" S., 

 long. 73° 46' 0" W. Depth 245 fathoms. Blue mud. Bottom temperature 46° - Fahr. ; 

 surface temperature 50°"0 Fahr. 



Remarks. — The peculiar skin-covered papillae or spinelets, regarded by Danielssen and 

 Koren 1 as sessile pedicellarise in their admirable description of Bathybiaster pallidus, 

 seldom seem in this species to appear so pedicellaria-like, or to be so highly specialised, as 

 those described in the North-Atlantic form. I have therefore refrained from speaking 

 of them definitely as pedicellariae in the foregoing description. When, however, the 

 voluminous membranous sac which invests each papilla or spinelet is folded, or injured 

 at the extremity by slight breakage, the superficial resemblance is very striking to the 

 structures described by the Norwegian naturalists. In some of the examples before me, 

 the injury to the sac (in the form of a transverse slit) appears to have taken place during 

 the life of the animal, probably by abrasion when passing over some rough surface, and 

 the margins of the break are somewhat thickened, as if during subsequent healing. 



The median spinelet in the furrow series of the adambulacral armature is not so highly 

 specialised in the Southern as in the Northern form. It distinctly simulates, however, its 

 character, the spinelet being covered with an extensive sac in which sometimes a supple- 

 mentary calcareous lamina is present. The papulae on the paxillar area may, under 

 favourable circumstances, be well seen in the Southern form. 



Notwithstanding these differences, after reviewing its structure as a whole, I feel Httle 

 hesitation in referring the present species to Danielssen and Koren 's well-defined genus 

 Bathybiaster. 



la. Bathybiaster loripes, var. obesa, nov. 



In a large series of examples from Kerguelen and Heard Island several small variations 

 in detail may be noticed, which from their constancy appear worthy of special recognition. 



1 Loc. «'<.,pp. 90-92. 



