324 OSTREAD.E. 



the featm-es of their shells, whilst under Anomia ephippium 

 we present his observations on the animal, all resulting in 

 inducing that eminent observer to hold to the specific 

 unity of all our British forms : — 



" With regard to the young, or dwarf A. ephippium, 

 the A. squamula, A. aculeata, and A. striolata, often 

 crowded in groups of fifteen or twenty individuals on a 

 single Pecten opercularis, I have not a doubt of their being 

 mere varieties of A . ephippium ; all these, often adopt the 

 markings of the substances on which they are fixed, and as 

 often show an entire disregard thereto, though they all 

 more or less invariably maintain the only true distinctive 

 character of the type, the decided squamose appearance, 

 which is never lost, whatever other markings there may 

 be. I have seen shells combining all the supposed distinc- 

 tive marks of each species or variety centred in one indi- 

 vidual, in which the decided smooth glossy A. squamula 

 commenced the umbonal part of the structure, gradually, 

 for the middle region, gliding into the squamous A. 

 ephippium, and dividing the basal portion, right and left, 

 the one, into the spinous asperities of A. aculeata, the 

 other, into the delicate smooth lines or striuloe of A. 

 striolata. Nothing is more common than to see shells 

 half squamula and half ephippium, half A. aculeata and 

 half A. striolata, and other admixtures of the characters 

 of two or three supposed species, on the same shell. These 

 facts prove, that the various markings, ribs, strise, &c, do 

 not always, as it were, by reflexion take the markings of 

 the substances on which they are fixed. All the last four 

 dwarf varieties of A. ephippium, are also found at the 

 roots of Alga and Fuci, but they, like their brethren on 

 shells, present, in the same individual, similar discrepancies 

 of colour, and admixture of characters. 



