324 DR. O. BOETTGER ON NEW CLAUSILIjE. [May I, 



Plate XXXII. 



Fig. 1. Padeirima Jchtgii (£ , p. 305. 



2. dharma, n. Bp., §, p. 306. 



3. indigofera, n. sp., (j', p. 306. 



4. macdellandii, n. sp., $, p. 308. 



6. Isamia midamus (j' , p. 312. 



6. Pademma 2>embertonii, n. sp,, J . p. 308. 



7. Isamia alopia S . p. 313. 



8. Tiruna roepstorffii, n. sp., cJ, p. 316. 



2. On new Clausilics from the Levant, collected by Vice- 

 Admiral T. Spratt, E.N. By Dr. O. Boettger, Frank- 

 fort-on-the-Main\ 



[Received April 10, 1883.] 



(Plates XXXIII. & XXXIV.) 



In 1878, in a dissertation entitled 'Monographic der Clausilien- 

 section Albinat-ia,' I tried to show that scarcely one of the more known 

 genera of land-shells presents us such instances of restricted local dis- 

 tribution as the section of the " fair white ones " of Clausilia, and 

 that through this strange restriction of habitat these forms of shells, 

 isolated for a long time upon generally unfrequented islands, have 

 deviated from their primitive type already so far that we must 

 acknowledge them to be distinct and now independent species. Of a 

 great number, especially of the island-species, there is evidence 

 sufficient to indicate the prototype with more or less certainty, and 

 that above all others O. carulea, For., or its ancestor seems to be 

 the primary form for a great number of varieties or allied species. 

 In no group is the limitation of the definitions " species, subspecies, 

 and variety " m.ore delicate and more difficult than here, because it 

 seems to depend only on the time, or, rather, on the earlier or later 

 age of the immigration or isolation, whether a form has developed 

 already into a so-called " good species " or not. Also, if in an earlier 

 time, and then again in a more recent period, the same species has • 

 immigrated from a neighbouring island into another island, then it 

 may happen, as we see now in the island of Amurgo, that two clearly 

 distinct species, 0. amorgia, Bttg., and C. ccerulea. For., arise, which 

 are both derived from one and the same ancestor, viz. from a form 

 doubtless quite near to the present C. ccerulea. 



It is evident that, in producing the astonishing variety of species 

 and forms of Clausilia in the Greek islands, "isolation " was one of 

 the principal factors, and that the question about " struggle for hfe" 

 or " natural selection " was but secondary to it. 



The following descriptions of a great number of new sjiecies, 

 varieties, and forms of Greek Clausilicd will give us new grounds and 

 proofs to illustrate these short theoretical reflections. 



With the knowledge of these new forms we advance more and 

 more in the science of the geographical distribution of this genus ; 

 ' Oommunicated by Vice-Admiral T. Spratt, E.N., F.E.S., F.Z.S. 



