272 



ECHIN0DERM8 OF THE BRITISH ISLES 



1. Cidaris cidaris (Liiinaeus). (Figs. 149, 150, 1-2, 151.) 



(Syii, Echinus cidaris Linnaeus ; Cidaris papillala Leske , 

 Cidaris hystrix Lamk. ; Dorocidaris jmpillata (Leske) A. 

 Agassiz.) 



Primary tubercles not crenulate. Ambulacral areas with four 

 regular series of tubercles (at least in the larger specimens). 

 Apical system large, about half the horizontal diameter of the 

 test ; oculars may be partly in contact with the joeriproct. 

 Genital pores not very large. Primary spines slender, about 



Fig. 151. 



-Cidaris cidaris ; from the oral side. Somewhat diminished. 

 (After Koehler, Echinod. Faune de France.) 



twice the diameter of the test. Colour in life yellowish or greyish- 

 white. The collar of the primary spines of a faint pinkish tint. 

 Reaches a considerable size, up to ca. 65 mm. horizontal diameter 

 of test. 



It lives on all sorts of bottom ; is often brought ujd on the 

 hooks of the fishermen. The larva (Fig. 152) is a typical Echino- 

 pluteus with a posterior transverse rod, but no posterolateral 

 arms. Postoral and postero-dorsal rods fenestrated. 



In British seas this species is very common along the west 

 coast of Ireland and in the Faroe Channel, in ca. 150-ca. 1250 m. 

 (it is recorded from both the Rockall and the Lousy Bank). It 



