60 PROCEEDINGS OF THK MALACOLOGICAL SOCIETY. 



has merely been turned over from its more central normal position ; 

 the flexures shown are found pretty uniformly. 



Mr. W. Moss has most kindly lent me, and allowed me to figure, 

 a radula from his collection inscribed " Hy. glabra, Studer. Per 

 Prof. Simroth. Leipsic. 28/9/98. 470." The dentition of this is 

 shown in Fig. 4. There is no need of detailed description to prove 

 that this is not an ordinary British Vitrea. The genitalia of the 

 same specimen have also been lent me by Mr. Moss, and are figured 

 here (Fig. 7). (The flexures of the male side and of the duct of the 

 spermatheca are partially accidental.) I have no doubt that Mr. Moss 

 was right in the opinion which he expressed to me in 1897, to the 

 effect that the Anglesey ^glabra'' (which I have also studied in their 

 native land) are near to, but not identical with, this form. 



It appears to me that according to the anatomical characters the 

 VitrecB of this group may be arranged in a series of couples, somewhat 

 after this manner : — 



lucida vera, ? affinities with olivetorum group. 

 JDrapanialdi ^.uA glabra (Fig. 4). 

 hibernica and Scharffi. 

 cellaria and Bogersi. 

 helvetica and alliaria. 



This may of course be purely artificial, but it is based on a general 

 consideration of the variable points. It is worth noting that the species 

 above enumerated may be distinguished by comparison of their basal 

 plates. In order to see these clearly and with certainty they should 

 be stained, and the preparation mounted in Canada balsam. The stain 

 of carbol thionin (which is very convenient for quick work) will keep 

 in glycerine, for a temporary mount, for a few weeks only. 



I am very willing to examine any British specimens that may be 

 supposed to be true V. helvetica, Blum. They are best sent in a fresh 

 condition. This paper ought not to close without a small word of 

 thanks to our President for observing and maintaining the distinctness 

 of V. helvetica and V. Rogersi. 



EEFERENCE TO ILLUSTRATIONS. 

 Fig. 1. Radula of Vitrea Rogersi, Woodward. (Westerham.) 

 ,, 2. Radula of Vitrea' helvetica, Blum. (Solothurn co-type; Mr. Kennard's 



specimen.) 

 ,, 3. Part of radula of Vitrea helvetica, Blum. (Solothurn co-type; British 



Museum specimen.) 

 ,, 4. Radula of Vitrea glabra, Studer. (From Professor Simroth, Leipsic; 



lent by Mr. W. Moss.) 

 ,, 5. Genitalia of No. 2. 

 ,, 6. Genitalia of No. 1. 

 ,, 7. Genitalia of No. 4. 

 ^'' The magnification of Nos. 1, 2, and 4 may be ascertained from the scale ; that of 

 No. 3 is slightly greater, it ha-ving been necessary to employ a different objective. 



