346 Mr. R. B. Newton on the Necessity for the 



of Mtiller. No notice, however, is made by this author to the 

 preoccupation of the generic name in 1799, and we can only 

 infer that Draparnaud was ignorant of its existence. 



We must go back now some considerable time, to 1789, 

 when William Coxe published his ' Travels in Switzerland,' 

 containing natural-history information grouped together under 

 the subsidiary title of " Faunula Helvetica," in which is a 

 section called " Vermes," written by Bernhard Studer (vol. iii. 

 pp. 384-392). This has evidently been a rai-e work to 

 consult, as so few authors have referred to it in their treatises. 

 It may be useful to state that a fine copy exists in the General 

 Library of the Natural-History Museum, and from this I now 

 make a quotation which has an important bearing on our 

 subject {vide p. 388) : — 



" POMATIAS, Studer, MS. 



" Vermis cochleatus, tentacuUs cluohus linearibus^ oculis ad 

 basin externe. 



"P. ELEGANS. Neritaelejans. Miill. 363. List. Ang. t. 2. 

 fig. 5. Syn. t. 27. f. 2o. 



L'Elegante striee, Fr. Die Feingestrickte Deckel-schenke, 

 Ger. Nerite-Pomatias. 



"P. variegatus. A new species." 



Here, then, we have every legitimate reason for keeping in 

 use Studer's Fomatias, 1789, the type of which is the same as 

 that adopted by Draparnaud for his Cyclosioma in 1801. 



In 1820 (Syst. Verz. Schweizer-Conchylien, p. 21) Bernard 

 Studer thought fit to recall his Pornatias and to use Cyclo- 

 stoma as understood by Dra])arnaud. This we cannot admit, 

 as his genus of 1789 Avas accompanied by a perfectly good 

 description for those days and a reference made to a properly 

 recognized type. It is, I think, an understood rule that a 

 genus once established cannot afterwards be withdrawn unless 

 its preoccupation can be proved. 



Hartmann, in 1821 ('' Syst. Erd- u. Sussw.-Gasteropoden 

 Europa," in Sturm's Deutsch. Fauna, vol. vi, part 5, pp. 34 

 and 49), apparently ignorant of Studer's work of 1789, 

 describes another Pornatias^ and uses Cyclosioma imtulum^ 

 Draparnaud, for its type. It is quite obvious then that the 

 use of Hartmann's genus must be discontinued and another 

 substituted, for which I propose Hartmatmia. 



