SOME LITTORAL TROCHID.E AND LITTORINIDJE IN CARDIGAN BAY. 115- 



LlTTORINID.^. 



(6) Littorina liUorea (Linnaeus). 



(7) L. neritoides (Linnseus). 



(8) L. ohtusata (Linnaeus). 



(9) L. rudis (Maton). 



General Distribution. 



(1) G. cineraria. — ^This species is rare throughout the whole of the 

 region examined. Two large living specimens were obtained after 

 careful search, in the coves at Gwbert ; these coves are situated sea- 

 v>'ard of the bar, and their general fauna is rich (for Cardigan Bay). 

 Two small specimens were also found, under stones about eight miles 

 south of Aberystwyth. Dead shells are not infrequent, so that this 

 species may be more abundant below tide marks. 



(2) G. umbilicata is, in certain districts, exceedingly abundant ; but 

 at Gwbert, in the coves above mentioned, I found but two. In New Quay 

 Bay it abounds, also locally from Llanrhystyd (and probably between 

 there and New Quay) to within some two miles of the Biver Ystwyth, 

 where it gradually dies out. Further north it reappears near Towyn 

 to the north of the Dysynni. It is abundant about Mochras, and occurs 

 at Y-Gamlas on the Zostera beds beyond Pwllheli. There it is accom- 

 panied by (3) G. magus, the only locality for this fine species that has 

 so far been noted in the Bay. 



(4) M. crassa has very much the same distribution as G. umbilicata, 

 but its range is more restricted, and always lies within the area occupied 

 by that species. Both are often exceedingly abundant for considerable 

 distances. 



(5) C. zizyphinus.—Bo far only one small living specimen has been 

 recorded, and that at Aberystwyth, where no other species of the Tro- 

 chidae exist. It probably occurs in deeper water. 



(6) Littorina Uttorea has a wide distribution, but is more especially 

 abmidant and much larger in certain places. 



(7) L. neritoides is, as elsewhere, very local. Its distribution around 

 the Bay appears to be quite normal and to be governed by its usual 

 requirements ; a rocky foreshore, affording crevices just above high- 

 water mark, and not exposed to the midday sun and the resulting desic- 

 cation. Given these conditions, it often will occur in very restricted 

 areas. South of Aberystwyth, the foreshore for considerable distances 

 is chiefly smooth rock, with a steep seaward inclination. One or two 

 large squared masses of fallen cliff are situated just about high-water 



