302 Royal Society : — 



CiDARIDiE. 



Cidaris, Lamarck. 



1. C. papillata, Ijeske. 



Occurs in enormous numbers on gravel at depths of from 100 to 

 400 fathoms, from Fseroe to Gibraltar, and small-sized examples 

 are frequent down to 1000 fathoms. This is a variable species, 

 and every possible link may be shown between the typical C. papillata, 

 Leske, and C. hystriv. Lam. I have no hesitation, after examining 

 many hundreds of specimens, in fusing the two forms into one 

 species. 



2. C. affinis, Stokes. 



This is a pretty little species, and apparently distinct, although it is 

 sometimes not easy to draw the line between it and small forms of 

 C. papillata. It occurs abundantly in the Mediterranean, and locally 

 off the coast of Portugal. 



For odd aj- is, Desor. 



This genus was established by Desor chiefly on a character which I 

 caunot regard as of great importance, and which is absent in the 

 present species, a row of small holes surrounding the tubercles of the 

 primary spines in the scrobicular arese. From the description these 

 holes seem to be nothing more than complete perforations, owing 

 to imperfect calcification, in the position of the depressions which 

 frequently occur in the scrobiculee of the Cidaridse for the insertion 

 of the muscles of the spines. Along with this character, however, 

 there were some others of greater value, a very remarkable paddle- 

 like form of the spines surrounding the mouth, and a tendency to 

 coalescence in the scrobicular arese. These characters are well marked 

 in the species described. This genus has hitherto only been found 

 fossil — a few detached plates and some of the characteristic spines in 

 the Nummulitic beds of Verona and Biarritz, and some spines referred 

 to the genus, on account of their having the same singular form, in the 

 Lower Oolite of Frick. 



1. P. purpurata, n. sp. 



Four examples from depths of from 500 to 600 fathoms off the Butt 

 of the Lews. 



ECHINOTHURIDiE. 



I think it due to the memory of the late Dr. S. P. Woodward to 

 adopt as the type of this very distinct and remarkable family the 

 genus EcMiiothuria, which he described with singular sagacity from 

 one or two imperfect specimens from the White Chalk. The Echino- 

 thuridse are regular urchins with depressed tests, rendered perfectly 

 flexible by the whole of the plates, both ambulacral and interambu- 

 lacral. being arranged in imbricating rows, the interambulacral plates 

 overlapping one another from the apex to the mouth, and the ambu- 

 lacral plates in the opposite direction. The margin of the peristome 

 is entire, and the peristomial membrane is covered with imbricated 



