196 PROCEEDINGS OF THE 



in the place at all where these are obtained, you will be sure 

 to find them ensconced between their layers. 



I have frequently remarked that the land shells generally 

 prefer a smooth, clean, and hard surface, to one overgrown with 

 lichens and moss, and have no hesitation in saying, that in the 

 former situation fifty specimens could be found for one in the 

 latter. Instinct seems to impress the terrestrial Pulmonohranclis 

 with the necessity of economizing their shme, and also to teach 

 them that the best way to do so is by avoiding porous and 

 uneven surfaces, and frequenting those that are solid, smooth, 

 and damp, the latter implying shady places. 



Before concluding, I cannot avoid directing your attention 

 specially to what you must have observed from the general 

 remarks already made — viz., to the great number and rarity 

 of many of the species found in Auchentorlie Glen, and all at its 

 lower part. These are Zonites alliaria, cellaria, radiatula, crystal- 

 linus, and fulvus; Helix nemwalis, fusca, aculeafa, and lamellata; 

 Carychmrii minimum, Clausilia rugosa, Pupa timbilicata, Bulimiia 

 obscurus, and Balia perversa or fragilis;* while, in the immediate 

 locality of the glen — viz., at Henry Bell's monument, we have 

 Helix aspersa and rnfescens, in all, sixteen species. Yet, while it is 

 so rich in species, there is a wonderful paucity of individuals, as, 

 for example, in three excursions, I only found three specimens 

 of H. aculeata, two of B. ohscurns, one of H. fusca, and one of 

 Bulla fragilis. 



I may also remark that there are four species in the collection 

 which Jeffreys does not mention as occurring in Scotland — viz., 

 Cyclas lacustris, Limnoea auricularia, Limncea glabra, and Helix 

 rnfescens. 



* Since writing this paper I have found on more minute examination 

 that the specimen of Balici fragilis referred to, is a somewhat doubtful 

 one, and apjjears either to be an abnormal form of Balia (there being only 

 a single indigenous species of that genUs), or an abnormal form of Clausilia 

 ruf/osa, or a variety of 6^. rw/osa, {)robably duhia; or a species differing from 

 Clausilia rugosa, probably " JiuljjJiii." It would be easy to determine whether 

 it was a Balia or Clausilia by breaking the shell and observing whether" 

 it had a clausilium, which is absent in Balia, but unfortunately there is only 

 a single specimen, so that we must either decide from external appearances 

 or destroy the shell. But however this may be, one characteristic specimen 

 of Balia has recently been found in Auchentorlie Glen, thus maintaining the 

 number of species which I stated is to be obtained there, and were the features 

 of this undetermined individual properly studied, it is possible that it might 

 add another to the number. 



