228 



THE BRITISH NATURALIST. 



CNOVEMBER 



habitually burrow into the little knobs of moss on these walls, and 

 after getting well in, they apparently proceed to hollow out the tuft as 

 a means of protection and sustenance, though some tips are always 

 noticeable. Balea from its smaller size seems to be more successful in 

 escaping the final effects of the solar influence, though frequently 

 bleached at the apex. On detaching these small tufts of moss carefully, 

 youfind many of them a mere shell, with families of Clausilia and Balea 

 packed tightly together inside, as often as not fellow-lodgers. 



In some species of the marine genus Etdima, it is the usual thing to 

 find the shells thus truncated, nor does any species of Eulima (within 

 '■'Dr. Jeffreys' experience) actually inhabit the top whorls even when 

 intact. Here, however, the decollation seems to take place more 

 arbitrarily both in the case of species and amongst individuals of a 

 species, and of course the only parallel intended to be adduced is one 

 of occurrence. One haul of the dredge off Guernsey this summer 

 contained seven live adults of Eulima polita L. (the most commonly 

 decollate Eulima) and of these 3 were absolutely faultless and 4 had 

 replaced their beautifully tapering apices by the usual flat shelly plate. 

 As a purely accidental loss, I have noticed the feature of decollation 

 in several species of Trochus (e.g., zizyphinus and umbilieatus), showing 

 their capability to live thus curtailed. Compare Jeffreys' record of a 

 Etdima polita living with only three whorls left. 



To return to terrestrial forms, I may mention that during a consider- 

 able experience of Clausilia Rolphii I have never found a decollate 

 specimen, this being entirely a retiring and ground-loving species. Of 

 C. laminata and C. biplicata I cannot speak with much knowledge, and 

 shall be grateful for other observers' experience. On the other hand 

 I can cite several non-British species that throw light on this subject, 

 for instance, that common North Italian shell, C. itala, Marts., which 

 swarms on walls and faces of rock round Lake Como, is frequently 

 decollate, and C. parvnla Stud., with rather more retiring habits, 

 occasionally presents the same variation in France; whilst any 

 conchologist who pays the inevitable visit to the Glacier Garden at 

 Lucerne will not fail to note (juite a number of decollate shells amongst 

 the stores of C. cvucidta Stud., C. parvnla Stud., and C. plicata Drap. 

 that he sweeps off the rocks with such avidity. 



Jeff. B.C. Vol. iv, p. 204. 



