76 



NATURAL HISTORY OF OUR SHORES 



They have no " Aristotle's lantern," but a scoop-like 

 projection of the test on the under side just a little behind 

 their anterior the wide end. 



The spines, instead of being " spine-shaped " and radiat- 

 ing on all sides, are of nearly equal thickness all through, 



Fig. 31. Spatangus purpureus. \ Natural size 



and they lie pretty well all in one direction that is, they 

 slope back, like the hair on a terrier dog. 



The largest species on our shores is Spatangus purpureus 

 (Figs. 31 and 32). It is about six inches in length and four 

 or five in breadth, by about two and a half inches thick 

 in mid body. The colour is purplish brown, and purple 

 (hence " purpureus ") seems to pervade the animal through- 



