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



actinal spine on the adambulacral plates ; and behind this, on the outer part of the plate, 

 there are three or four minute, thorn-like spinelets, irregularly placed. The tumid charac- 

 ter of the infero-marginal plates and of the mouth-plates give a very ornate appearance to 

 the actinal aspect of this species. 



The actinal intermediate plates are comparatively rather large, but not more than ten 

 to twelve are present in each interradial area ; they are slightly tumid, and bear near 

 their centre three or four small thorn-like spinelets. 



The anus is subcentral and very distinct, and a punctured tube is seen protruding ; 

 the surrounding paxillas are not distinguishable in any way from the others in that region 

 of the disk. 



The papular groups at the base of the rays are small, with eight papulae in each ; 

 these are arranged in two lateral series of three, with a medium series of two, which 

 are larger and wider apart. The paxillae between and in the neighbourhood of the 

 papulee are precisely similar to the others on the abactinal area. 



The madreporiform body, which is small, circular, and slightly convex, is situated 

 nearly midway between the centre and the extreme margin, but rather nearer the latter. 

 Its surface is grooved with numerous comparatively fine, deeply incised, convoluted and 

 radiating striations ; and there is one large paxilla on its adcentral side larger than any 

 of the others on the abactinal area. 



Colour in alcohol, a bleached yellowish white. 



Young Phase. — There is a young example (from Station 76) which measures E = 14 + 

 mm. (the terminal plate being unfortunately broken from every ray), and r = 3'5 mm. 

 The paxillse are remarkably large as compared with the size of the animal. The marginal 

 plates are large and have the characters of the adult. Thirteen supero -marginal plates are 

 present between the median interradial line and the broken extremity, and from this 

 region, I believe, only the odd terminal plate is missing. The lateral spine on the infero- 

 marginal plates is remarkably small and inconspicuous, and only a little larger than the rest 

 of the spinulation of the plate ; whilst the spine on the supero-marginal plate, though very 

 small, is much more robust — an opposite proportion to what obtains in the adult stage. 

 The adambulacral plates are large, elongate, and separated by wide interspaces occupied 

 by ligament. The furrow series of spines has fully assumed the palmate character of the 

 adult, and the single large spine on the actinal surface of the plate is remarkably robust. 

 There are only four intermediate or ventral plates in each actinal interradial area, and the 

 inner pair are much the largest, in fact larger than any of the adambulacral plates. 

 On their surface are a few isolated thornlets. The actinal surface generally already shows 

 traces of the tumid character of the plates, which forms at once an ornate and a dis- 

 tiueuishino; feature of the adult form. 



Localities. — Station 76. Between the islands of San Miguel and Pico (Azores). 

 July 3, 1873. Lat. 38° 11' 0" N., long. 27° 9' 0" W. Depth 900 fathoms. Pteropod 

 ooze. Bottom temperature 40°"0 Fahr. ; surface temperature 70°*0 Fahr. 



