NUCULA. 145 



every coast from the Faroe Isles to Sicily and the 

 iEgean, and also the North African side of the Medi- 

 terranean. 



Mr. Clark says that the animal is timid, and therefore 

 difficult to observe. When in motion, its foot becomes 

 a flat and nearly circular disk; its progress is not 

 direct, but, turning round as on a pivot, its path de- 

 scribes an irregular ellipse. M. Gay of Toulon informs 

 me that he constantly finds empty but perfect shells, 

 with the epidermis entire, inside starfishes, which would 

 therefore seem to have the power of killing the animal 

 and sucking it out of the shell,' after swallowing it. 

 Petiver called this pretty kind the " silver cockle "; and 

 it is a favourite prize of children when they gather their 

 sea-side harvest in the autumn, 



" On the beached margent of the sea." 



It may be 



"The shell from the bright golden sands of the ocean, 

 Which the emerald waves at your feet gladly threw," 



alluded to by Keats in his delightful sonnet to some 

 ladies. Specimens are now and then found more convex 

 than others, even from the same locality. Occasionally 

 the lines of growth are raised ; and where they cross the 

 longitudinal strise a decussated appearance is the result. 

 My first impression, that the N. radiata of Forbes 

 and Hanley was a distinct species, has yielded to a con- 

 trary conviction, in consequence of having compared 

 numerous specimens of all ages and sizes from various 

 places ; and I feel myself bound to reunite it with 

 N. nucleus. Typical, and even ordinary specimens of 

 each form cannot be confounded with each other ; but 

 I have some from Plymouth and Tenby, which may be 

 referred to either form. The grounds of supposed dif- 

 ference are the comparative size, shape, convexity, and 



H 



