REPORT ON THE TESTACEOUS MOLLUSC A. 243 



Thracia papyracca is often thrown up on the beach at 

 Penmaenmawr in considerable numbers, but I have never 

 found it at home (D.). 



Mya truncata lives in the channels below Bangor, in stink- 

 ing black mud, growing large, but discoloured in the shell. 



A form, greatly abbreviated, occurs within the influence 

 of the Conway River. 



Sometimes large numbers are thrown up by the sea on 

 Colwyn sands, with the chitinous siphon cases quite perfect, 

 but the animal altogether gone. 



Saxicava rugosa, which is extraordinarily abundant in 

 the limestone on Puffin Island and Anglesey tidal rocks, may 

 sometimes be dredged amongst dead shells in Conway Bay of 

 a large size and free growth. 



Pholas crispata. This shell occurs rarely at Southport, 

 and more frequently from Point of Ayr to Rhyl and Abergele 

 as very worn dead valves of large size. It lives in the red 

 sandstone rock at Hilbre Island, where it grows to about two 

 inches in length. 



A prolonged search at last found this animal living in 

 abundance, and of very great size, in coarse sandy mud near 

 Beaumaris. Specimens measuring 3*4 inches are not un- 

 common, and 3*7 inches and 3*8 inches have occurred to me. 

 I have found shells of this species, subfossil, at Bracklesham 

 Bay 4*2 inches long (D.). 



Pholas Candida. A curious distribution of valves along 

 the shore from Southport past Formby Point was noticed. 

 North of the Point, one valve was common and the other 

 rare; southward, the latter valve was the common one. 

 Experiment proved that this separation was probably due to 

 the behaviour of a shell, so peculiarly shaped and balanced, 

 in the prevailing tidal flux, as it brought the valves up 

 from low-water. Great colonies in blue clay at low-water at 

 Blackpool. Sometimes eaten boiled. 



