74 NATURAL HISTORY OF OUR SHORES 



Still in the littoral zone, and under boulders where there 

 is space, occurs the pretty Echinus lividus. It is larger 

 than the last, and is of a more robust structure, the spines 

 stout and very sharp. In colour it varies ; some are of 

 uniform deep purple, others of a bright green, and this does 

 not seem to be due to habitat, for both kinds can be hauled 

 out from under the same boulder. This species is shown 

 in Fig. 30. It is said that it excavates for itself hollows in 

 the stone, and it has been speculated upon as to whether it 

 is by a mechanical or a chemical process that it bores. I 

 am not qualified to express an opinion on this matter, for 

 although I have dragged out from their hiding, and ex- 

 amined^ some bushels of them I have no evidence of their 

 " boring." The rocks here are granite and diorite, and into 

 these I am,- quite sure that they do not bore, although they 

 avail themselves of any existing hollow. 



In loose shell gravel and broken stone, sometimes in the 

 littoral but more usually in deeper water, is the large 

 Echinus esculentus, used on many parts of the Continent 

 as an article of food, under the name of Chataigne de mer 

 ("Sea-chestnut"). 



This species grows to the size of an ordinary pudding- 

 basin that is, from four to six inches in diameter. Its 

 colour is usually white, but the spines are rather sparsely 

 distributed, leaving the test visible between, so that a pale 

 pink is the effect. Sometimes the spines are lightly tipped 

 with violet. Closely allied, unless indeed they are but 

 varieties, are Echinus melo and Echinus acutus. The first 

 of these, as its name implies, is melon-shaped. The latter 

 has a tendency to a conical form. In colour, disposition of 

 spines, etc., they are as the one just described. 



A splendid species, found in the Channel Islands perhaps 

 on the English shore as well, although I have not heard of 

 it is one termed Sphcerechinus brevispinosus. It is much 

 more robust than those just described ; the spines are short, 



