150 CIDARITES. 



Echinus esculentus, Pennant, Brit. Zool. IV. p. 67, No. 74, t. xxxiv. f. 74. 



Fleming, Brit. An. p. 478. 

 Echinus globiformis, Lam. 1 Edit. II. p. 44 ; 2 Edit. III. p. 3G0. 



That the common Sea-Urchin of our shores is the 

 Echinus splmra of Muller I have no doubt ; and that it is 

 not the Echinus esculentus of the Mediterranean I am 

 equally certain, having compared a specimen of the latter, 

 kindly sent me by Mr. Ball, with our own species. Blain- 

 ville's figure of the true esculentus is good, and will enable 

 the naturalist to distinguish that animal should it occur 

 on our shores. It differs from all our native species in 

 having four pairs of pores in each row, and the ridges on 

 the spines crenated. It is probable the Echinus melo of 

 Continental authors is identical with the Splueva, but 

 Muller's name has the priority and must be retained. 



The common Egg-Urchin varies much in form. It is 

 sometimes almost globose, sometimes much depressed ; and 

 the extreme variations which it presents have led many 

 zoologists to suppose that several species were included 

 under one name. The essential characters of the species 

 are, however, constant in all. The variation is merely of 

 proportion. It seems to be arbitrary, and not depending 

 on locality, as the following comparison of the sizes of 

 specimens selected at random from various localities will 

 show. 



The essential specific characters depend on the arrange- 

 ment of the tubercles which bear the spines, on the spines 



