166 



ECHINOIDEA. 



from their great size and the distinctness of their bright yellow 

 colour from the purplish test ; sometimes they may be remarkable 

 for their size only, and sometimes they may be quite inconspicuous. 

 The general coloration, again, varies witbin wide limits ; the general 

 facies may be a universal purple, but it may be brown, or yellowish, 

 or whitish. So, again, the form of the test is sometimes well rounded, 

 sometimes flattened ; the cordiform contour may be qualified, so that 

 some specimens are more truncated and some more evenly rounded 

 than others. 



The ambulacral petals are wide and each of the antero-lateral pair 

 s longer than the postero-lateral ; the pores in the neighbourhood 

 of the apex are quite small, and the reduction in size is most marked 

 and most extensive in the anterior half of the antero-lateral petals ; 

 the inner pore of a pair is always smaller than the outer. Anterior 

 groove rather wide. In the apical area the madreporite is very 

 prominent. The mouth is wide, and the lower lip has a rounded 

 angle. The subanal fasciole is well-marked, broad, with a wide and 

 deep angle on the side nearer the anus. The anus is transversely 

 oval, looks backwards and downwards. The tubercles vary con- 

 siderably in size ; the largest are found on the dorsal surface, and 

 chiefly between the petals ; a very few are found within the petals ; 



the 



granules forming the 



general covering of the upper surface 



of the test have a tendency to become smaller as the ambitus is 

 approached. 



On the ventral surface the tubercles are generally larger ; they 

 are smallest near the ambitus and largest in the region of the 

 mouth ; within the subanal fasciole the tubercles are smallest in the 

 narrowest region and largest in the wings on either side. 



There is some not inconsiderable variation in the breadth and 

 form of the petals ; the postero-lateral are sometimes almost oblong 

 instead of petaloid ; in young specimens the pores of a pair are not 

 markedly different in size ; while always wide the anterior groove 

 varies somewhat in depth. 



Greatest breadth of 



Distribution. East side of Atlantic from the Azores to Iceland ; 

 Bermuda ; North 8ea ; Mediterranean. 5-530 fnis. 



