DEAN AND TOMLIN : JAMlNIA TRIPI.ICATA IN SUFFOLK. 167 



Rossmassler's Pupa bigranata seems to be somewhat uncertain, 

 though personally we think that Jeffreys was correct in taking it to be 

 the bidentate form of muscorum. It may be well to point out, how- 

 ever, that the latter author, when he speaks of the denticle on the 

 columella, in describing the var. bigranata, means the parietal tooth. ^ 

 Fortunately we may in any case discard Rossmassler's name, as 

 reference to Draparnaud's^ original description of his Pupa marginata 

 shows that it refers to the bidentate form of muscorum, which may 

 therefore figure for the future on our list as var. marginata Draparnaud. 



We use in this paper the generic na.xne /aminia for convenience, as 

 being the name used by Dr. Chaster. 



Notes on some Shell Beaches and rare Cornish Marine Shells.— 



Mangilia rugulosa Ph. — I found three specimens of this shell in a small cove on 

 the right bank of the river and close to the mouth, near Padstow, in August, 1910. 

 This locality agrees with that given in Tregelles' List, viz., the parish of St. 

 Merryn, on the authority of the late W. V. Tellum. Mr. W. Hockin found it 

 here in 1865, this being the first record for the British Isles. Mangilia nebula var. 

 vittata Norm. —Mangilia Icevigata Jeff. — This very rare shell, according to Dr. G. F. 

 Tregelles' Lists, has been found at Scilly on a few occasions, but not on the main- 

 land. I procured a single specimen at Sennen Cove in April, 1910. Mangilia 

 nebula var. lavigata Ph. ( — M. Icevigata var. minor Jeff.) is far more common than 

 the above. I have found it at Falmouth, Sennen, Porthcurnow Cove, and near 

 Padstow. Mactra glauca Born. — Mr. J. W. Girdleston, of Carbis Bay, near St. 

 Ives, kindly allowed me to inspect several fine specimens of this rare shell, picked 

 up by him at Carbis Bay, Lelant, and Hayle. He told me that he used to find 

 large numbers of this species. Divaricella commutata Ph. — This shell also, Mr. 

 Girdleston informed me, used to occur in considerable quantities with Mactra 

 glauca. He kindly gave me two valves. It is interesting to note that these two 

 species are no longer found at the places mentioned, and not only so, but there 

 has been a general falling off in numbers of all species found at St. Ives Bay. Mr. 

 Girdleston, living on the spot, informed me that there was not now a hundredth- 

 part of the shells that there used to be. This was my experience also, during the 

 four periods (one extending over six weeks) in which I had these beaches under 

 observation. As a result of six years' close observation I am forced to the con- 

 clusion that a similar diminution in the number of shells cast up has taken place 

 in nearly every part of Cornwall. This is certainly the case at Falmouth. I have 

 data in the case of particular species which would prove this. For example, in 

 six years I found only one example of Aporrhais pes-pelecani at Falmouth. This 

 used to be common there. Any explanation of these facts would, I think, be of 

 very great interest. Dredging operations at Falmouth, Helford, and St. Ives have 

 caused me to conclude that this diminution is not confined to shells cast up. — 

 Alan Gardiner. {Read be/on the Society, Dec. 8th, 1915). 



Brit, Conch., vol. i., p. 250. 



Hist. Nat. des Moll. Terr, et Fluv. de la France (1805), p. 61. 



