270 s. goto: 



of the dorsal area, it might be said, reasoning from the analogy of Astro- 

 pecten, tliat no such apertm-e existed. The region is sometimes slightly pro- 

 truded in a low cone, sometimes slightly introvei-ted in the centre. 



" The madreporiform body is moderately large, subcircular, and situated 

 midway between the centre of tlio disk and the margin. The central area 

 of the body is abruptly elevated and occupied by one of the mulberry- 

 like masses of hemispherical granules similar to those on the tabulum of 

 the paxillte, and tliis again is surrounded by the marginal fringe of 

 spinelets (in fact a central, but sessile, paxilla) ; beneath this the striation- 

 f mi'ows, wliich are fine, may be seen radiating to the periphery of the body. 



" The ambulacral fm-rows are completely closed in by the adambulacral 

 plates and armatm-e when contracted. The tube-feet have conical tips when 

 extended, but which appear shghtly knob-hke when contracted. 



" No pedicellarisB of any kind are present. 



" Colour in alcohol, a brownish grey over the paxillar area ; marginal 

 plates and actinal sm'face a bleached yellowish wliite. 



" Ycning ^/^«sc. — In a small specimen from Station 203, measmiug 

 R=:22mm., r=6.5mm., the number of marginal plates is twenty-fom*, and 

 in general character this example accords in all points with the adult form, 

 the species being unmistakable. The remarkable webbed fringes are fully 

 developed, and the fm-rows between the marginal plates are veiy wide. 

 The number of spinelets in the paxillse and in the armature of the adam- 

 bulacral plates is rather less, esi^ecially on the attingent sides of the latter, 

 as might natm-ally be expected. The spinelets in the fmTOW series range 

 in number from fom- to six, according to position. On the larger paxillaî of 

 the disk, seldom more than six to nine marginal spinelets are present, and 

 not more than one or two central gi-anules ; along the ray five or six ap- 

 pears to be the normal number. The madreporiform body is relatively 

 nearer the margin tlian in the adult form. The centre of the abactinal 

 region is slightly inti'overted as in many Astropectinida3. The development 

 of the terminal (or ' ocular ') plate is interesting. In the yoimg stage re- 

 ferred to, the plate is divided along its entire median line, forming a more 

 or less wide and gaping channel, with the edges roimded, along which the 



