A Revised List of BrUish Echiiioidea. 405 



Subgenus Porocidaris, Desor. 



1854. Porocidaris, Desor, Synop.s. P^chin. foss, , p. 46. 

 1874. ,, Wyv. Tliomson, "Porcupine" Echin., Phil. Trans,, 



p. 726. 



" Ambulacra broad and straight ; pores wide apart, united by 

 a groove ; primary interradial tubercles with small . . . crenu- 

 lated mamelons." Five diamond-shaped o[)enings round the anal 

 region of the test, filled with chitinous membrane, through which 

 pass the oviducts ; " some spines flattened, with strongly serrated 

 edsfes." 



'is^ 



2. Cidaris purpurata (Wyville Thomson). 



1872. Porocidaris ;purpurata, Agassiz, Rev. Echin., pp. 152, 395, 



pi. i., figs. 37-41; pi. xxiv., fig. 11. 



1873. ,, ,, Wyv. Thomson, Depths of the Sea, 



p. 101. 



1874. ,, ,, Wyv. Thomson, "Porcupine" Echin., 



Phil. Trans., p. 725, pi. lix., figs. 14, 

 15 ; pi. Ixi. 



Diagnosis. 



Buccal membrane with imbricated scales, ten double rows of 

 ambulacral, perforated up to the edge of the mouth, with double 

 pores, in continuation of the pore-areas of the corona ; interambu- 

 lacral regions with imperforate scales. 



I have not seen a specimen of this species. 



Distribution. 



British Seas. — N.-W. of Lewis, warm area, "Porcupine" Exp, 

 (1869), Station 47, 542 fms. (Thomson, 1, 2). " Knight Errant" 

 Exp., St. 7, 530 fms. (Agassiz, 4). 



Other Localities. — None recorded. 



DIADEMATOIDA. 



EcHiNOTHURiiD.^, Wyville Thomson. 

 Test thin and flexible ; plates overlapping, ambulacral, and 

 interambulacral in opposite directions ; ambulacral pores trige- 

 minal, one pair penetrates the ambulacral plate itself, the others 

 two special accessory plates. 



2. Phormosoma, "Wyville Thomson. 



1874. Phormosoma, Wyv. Thomson, "Porcupine" Echin., Phil. Trans., 

 p. 732. 



