COOKE : ON THE GEKUS CLAUSILIA. 251 



mechanical causes may contribute to this result. The group Siciliaria, 

 peculiar to Sicily, contains many species remarkable for their latticed 

 ribbing, a feature characteristic of most of the group Agathylla. Yet, 

 while Agathylla adheres to steep rocks, Siciliaria is habitually found 

 under loose and flat stones, often decollated, and disfigured with clay. 

 I am inclined to attribute the frequent decollation of adult specimens 

 of this group to its particular habitat, and shall be surprised if 

 a common Himalayan species, Cylijidrophcedusa cylindrica (Pt'r.), 

 which is always decollated, does not live in a similar way. 



Two species at least, Ewphcedma tetsui, B. & S., from Hupe, and 

 Pirostoma ventricosa, Drap., from Nortli Europe, are known to be 

 ovoviviparous. 



Clausilia is intolerant of extreme cold, a fact which is indicated, not 

 only by its hibernation, even in temperate climates, but also by its 

 general geographical distribution. Early in September, 1913, I was 

 seeking a particular species of Alopia on the top of a mountain 

 between 6,000 and 7,000 feet high, in Roumania, and was dis- 

 appointed to find nothing but a few dead shells. At last I discovered 

 plenty of living specimens buried from 6 to 9 inches deep in the soil 

 at the foot of the rocks on which they ought to have been climbing, 

 and it then occurred to me that two or three days before an unusually 

 heavy snowfall had covered the range, and the shells must have 

 concluded that winter was upon them, and disappeared accordingly. 

 No doubt all Alopia whicli live at a high altitude (and one species 

 lives at the top of the Butschetsch, 8,230 feet) inter themselves 

 deeply in the earth or in the cracks of the cliffs during the winter 

 months. Albinaria jestivates by secreting a paper-like epiphragm, 

 by which it glues itself to the underlying rocks, and prevents evapora- 

 tion. Like many Xerophila and some Buliminus, it has a black body 

 beneath a white shell, a fact which no doubt serves some purpose in 

 the animal's economy. 



Piaget (45) has made some interesting investigations into the 

 altitude to which certain Swiss species can attain. He found that 

 parvula and ventricosa do not, as a rule, ascend higher than 1,500 m., 

 crnciata and plicatula than 1,700, while duhia and laminata can 

 sustain life at 1,850 m. In warm climates these altitudes are greatly 

 exceeded. Euphmdum xoaayeni, Stol., is recorded from Murree, 

 West Himalayas, at 9,000 feet, wliile Nenia raimondi, Phil., is found 

 in Peru at over 10,000 feet, in the Cordilleras. All these heights are 

 surpassed by sennaarie7i.ns, Pfr., which is stated by Bourguignat to 

 occur on the Abouna Yousef, in Abyssinia, at 4,024 m. 



The genus falls, geographically and conchologically, into three 

 great divisions : — 



I. Clausilia proper, inhabiting Europe, South-Western Asia, 

 North Africa, and the Madeira group. 

 II. Phadusa, inhabiting South and East Asia and certain of the 

 East Indian islands. 

 III. Nenia, inhabiting South America and one West Indian 

 island. 



