COOKE: DISTRIBUTION AND HABITS OF ALOFIA. 9S 



to extremes of variation. Thus, of the Alitida group, critica, Bielz, 

 fallax, Rossiu., stabilis, Zieg, are found everywhere, and the same is 

 the case with cana, Held, and plicata, Desh. {Laciniaria), marginata, 

 Zieg, transsylvanica, Zieg, and orthostoma, Menke (Marpessa), 

 latestriata, Bielz, and dtibia, Drap. {IpMgenia). Some of these forms 

 occur wherever an Alopia is found (I have a specimen of cana from 

 the top of the Butschetsch, 8,230 feet), and they are spread impartially 

 all over the district. 



3. Habits of Life and Food. — One notices that though all Alopias 

 live on limestone rocks, and nowhere else, there are certain difierences 

 of method in the various species. In the Krepatura, A. Fussiana, 

 var. insignis, is scattered in ones and twos on the perpendicular face 

 of the cliif, and seldom packs closely together. On the Donghavas, 

 A. IIaueri,\i\v. amligua, has similar habits, and a closely related form 

 from the Czukas is scattered over rocks, showing a special predilection, 

 which I have noticed in other groups, for bands of moist clay. 

 On the Tesla, A. glauca does not gather gregariously in cracks or 

 holes, but stands out singly on the face of the rock. The same is the 

 case with livida in the JVlalaj ester Schlucht, and with a form of whose 

 exact identity I am not quite certain, found on the Furnica in 

 Koumania. On the other hand, A. Fussiana, var. pruinosa, from 

 a similar locality to the east of the Kcinigstein, fairly astonished me 

 by its propensity for clotting together in masses at the foot of the 

 cliffs close to the ground. I first found a bunch of twenty-seven, 

 then another of sixty, and finally measured a space 2 feet long by 

 2i inches high, and counted on it over 200 living specimens, all adult. 

 A. Meschendotferi, on the Zeidnerberg, gathers in bunches in the 

 hollows of the limestone. On the top of the Piatra Mare A. canescens 

 is fairly abundant, but if you look on the rock faces you will hardlj- 

 find a single specimen, even in the shady cracks ; the species occurs 

 half buried in the grass at the foot of the rocks and under ledges 

 which are almost flush with the ground. 



The food of Alopia is, as a rule, minute mosses and lichens. There 

 is no doubt that the microscopic algse and vegetable organisms 

 occurring on the disintegrated limestone surfaces are also eaten by 

 them. On the conglomerate it can only find moss and lichen. I have 

 never found one on a green leaf. 



4. Variation in Size. — When large numbers of a given species are 

 examined, specimens will generally be found of a large and also of 

 a small form, in each case fully grown. The fact is very marked in 

 the case of livida from the Malaj ester Schlucht, glauca from the Tesla, 

 Kaueri, var. amhigua from the West Donghavas, plumbea from near 

 Kronstadt, Fussiana from the Kunigstein. In each of these cases the 

 larger form sometimes contains two whorls more than the shorter, and 

 the shell appears much finer and more fully developed. It seems 

 probable that this difference in size is not due to any cause marking 

 an optimum or pessimum of locality, or to any distinctions in the 

 conditions of foocl supply. One is more inclined to support a view ' 



^ Kiister, Die Binnenconcliylien Dahnatiens, p. 10. 



