328 ECHIN0DERM8 OF THE BRITISH ISLES 



1. ISpatamjus purjyureus O. Fr. Miiller. (Fig. 190.) 



(Syn. Spatangus meridionalis Risso.) 



Test broad, rather low, regularly arched on the upper side, flat 

 on the under side ; the mouth not much sunk. Labrum broadly 

 rounded (Fig. 192, 2). The area included by the subanal fasciole 

 very broad, ca. three times as broad as long (Fig. 193). Fairly 

 numerous large tubercles (spines) in the interambulacra on the 

 upper side of the test, but not in the ambulacra outside the 

 petaloid part. Colour violet, the long curved spines of the upper 



Fig. 190. — Spatangus purpureus ; naked test, from above. Nat. size. 



side lighter coloured, often whitish. The colour does not fade 

 in alcohol. Reaches a very considerable size, up to ca. 120 mm. 

 in length. 



It prefers a rather coarse sand or gravel bottom, in which it 

 lies wholly buried. The food consists of all sorts of bottom 

 particles and organisms {e.g. EcJiinocyamus pusillus), which it 

 picks out by means of its penicillate oral tube-feet. A form 

 living on muddy bottom (type locality off Lowestoft) is more 

 concave on the oral side than usual in the typical form and has 

 been distinguished as a separate variety, the Var. concava Khng- 

 hardt ; very probably this is, however, only an abnormal form, 



