EEPOKT ON THE ASTEKOLDEA. 45 



is one short, robust, conical spiue. Excepting one or two isolated granules or miliary 

 spinelets there are no other spinelets on the plates, though at first sight the pedicellariae, 

 which stand on the margin of the infero-marginal plates, might almost be cousidered to 

 belong to the adambulacral plates. 



The mouth-plates are large and rather prominent, and their armature consists of 

 a marginal series of about seven to ten short spinelets, the two innermost being much 

 the largest, whilst the others are subequal or decrease slightly in size as they recede from 

 the mouth. On the actinal surface of the plate there is usually a lineal series of small 

 conical spines running parallel to the suture, and in the interspace between these and 

 the marginal series there are one or more spines, one of which is much larger than the 

 others, and is the representative of the large spine on the actinal surface of the adam- 

 bulacral plates. There is frequently some irregularity in the disposition of these inner 

 spines. 



The actinal interradial areas are small, and occupied only by a few irregularly placed 

 intermediate plates ; the spinelets they bear are most of them modified into pedicellarise- 

 like bodies similar to those elsewhere found on this species. 



The anus is central and very distinct, with several larger spinelets surrounding its 

 margin. 



The madreporiform body is small but convex, and is usually less (but sometimes rather 

 more) than its own diameter distant from the margin. The striae are coarse and deeply 

 incised. 



The papular groups at the base of the rays are small and with not more than eight to 

 ten papulae in each. The paxillae amongst the group are small and modified in form, and 

 the crown is often represented only by the central spine. 



Colour in alcohol, a bleached greyish or yellowish white. 



Young Phase. — The smallest example (from Station 46) measures R=ll mm., 

 r = 25 mm., and is already so far characterised that it is scarcely too much to say that 

 it would be referred with but little hesitation to the species, even if found isolated. There 

 are twelve supero-marginal plates, and the spines borne on these and the infero-marginal 

 plates, though small, are tolerably robust in comparison to the size of the specimen. 

 Robust central spinelets are already present on a number of the paxillas, whilst the 

 encircling series, five or six in number, are mere conical thornlets radiating apart. There 

 are several large and fully developed pedicellariae on the abactinal paxillar area ; similar 

 large valvate pedicellariae, composed of four or five spines, are also present on the actinal 

 surface, chiefly in the actinal interradial areas, but also on the infero-marginal plates, 

 extending along the ray as far as the fourth or fifth plate, or occasionally further. There 

 are two if not more small intermediate plates in the actinal interradial areas. The 

 adambulacral plates have a furrow series of four or five spinelets, with or without an 

 incipient thornlet at the end of the series, and on the actinal surface of the plates is a 



