244 



COLOUR VARIETIES OF DONAX VARIEGATUS (Gmelin) 

 FROM THE CHANNEL ISLANDS. 



Bv R. WOODCOCK. 



(Read before the Society, M.arch 8th, 1911). 



Having collected marine mollusca in the Channel Islands for several 

 years, I have often noticed, wlien working the gravel banks at extreme 

 tide limits, that as soon as the tide turns the pretty Donax variegatus 

 has a curious habit of springing out of the gravel, which action close 

 observation has shewn to be caused by the contraction, followed by 

 a sudden expansion, of the somewhat large foot of these bivalves. 

 On certain favoured gravels, more especially on the south coast of 

 Jersey, it is quite possible to collect several of these Donax lying 

 thus exposed on the surface of a bed which a few moments ago was 

 bare of specimens; one has to gather them rapidly, as the tide runs 

 in so swiftly at this time. Their curious acrobatic habits interesting 

 me considerably, I determined to collect several in hopes of finding 

 varieties. Careful examination of the catch showed three distinct 

 colour variations in addition to the type. 



The beautiful var. tristis of Bucquoy, Dautzenberg, and Dollfus, 

 is a variety in which the umbones are of an exquisite purple tint, the 

 interior of the shell, and certain parts of the mollusc itself partaking 

 of this shade. These specimens when seen together with others 

 stand out very distinctly indeed. This variety usually occurs in com- 

 mon with the typical D. variegatus and var. aurea in the Laminarian 

 zone. I have found them in the proportion of fifteen to eighteen 

 of var. tristis to a hundred of the type. They are rather scarce and 

 seem to favour a more gritty gravel than var. laeta. 



Localities: — Royal, St. Clement's, and St. i\ubin's Bays, Jersey ; 

 Cobo and Rocquaine Bays, Guernsey. Mr. Tomlin informs me that 

 it also occurs commonly at Herm Island. 



Var. laeta Bucquoy, Dautzenberg, and Dollfus, occurs at the 

 lowest range in the Laminarian zone ; in fact, I have taken this form 

 in the Channel Islands solely from gravels which only dry during the 

 great tides of the spring and autumn equinox. They seem partial to 

 a sandier gravel than the other forms. In this variety, the umbones 

 are of a pretty pink tint, the interior of the valves being in most 

 cases yellow near the umbones, with a creamy white band around 

 the outer edge of the interior of the shell. 



Localities : — Royal, St. Clement's, and St. Aubin's Bays, Jersey. 

 1 have never yet succeeded in finding this beautiful form in any of 

 the other Channel Islands, but am, of course, not prepared to state 

 that they are local to Jersey gravels only in these islands, but they 



