39 



THE STATUS OF HELWELLA AND POLITA. 



By Dr. Henry A. Pilsbry. 

 Read 9th December, 1921. 



In the last number of these Proceedings the name Helicella 

 Ferussac was discussed by Gr. K. G-ude and B. B. Woodward. They 

 conclude that it should displace Polita or Hyalinia for the welJ- 

 known Zonitid genus typified by Helix cellaria, Miiller, and that it 

 caniaot be used for the Xerophilous Helices grouped under Helicella 

 by some authors, among them the present writer in the Manual of 

 Conchology, vol. ix. 



At the time that classification of Helices was published (1894-5), 

 we were working under the old rules of nomenclature. Type 

 species of composite genera were often selected by the method of 

 " elimination ". Now, under the international rules, we accept the 

 first subsequent designation of a genotype in such cases. This 

 change in the rules does not, I believe, affect the case of Helicella. 



Beck's list virtually restricted the group to Zonitid snails, and 

 other authors had used it for one part or another of Ferussac's 

 assemblage ; but Hartmann ^ was perhaps the first to expressly 

 state that Ferussac had included in Helicella many heterogeneous 

 species, and to restrict it to the group commonly known as XeropJiila. 

 Herrmannsen ^ evidently endorsed this restriction, as he cited 

 Hartmann's work, followed by " Typus : H. ericetorum, Miill.". 

 This was the earliest type designation, so far as I can ascertain. 

 According to Herrmannsen's table, p. 507 of his work, was issued 

 May 25, 1847. Gray's selection of H. cellaria as type of Helicella 

 was later, in November, 1847. Helicella should therefore remain 

 attached to the xeBDphile group of Helices, and not replace Polita. 



For the Zonitid group of H. cellaria I have preferred to use Polita 

 rather than Hyalinia. The names were proposed in the same 

 year, 1837, the relative dates unknown ; but Hyalinia would be 

 considered a homonym of Hyalina Schumacher, 1817, by mos^ 

 nomenclators. 



In the case of Petasina versus Euconulus we must accept the 

 change, hoping that it is the last for this genus. 



Some other decisions of this important paper seem to me open 

 to question, among them the substitution of Xeroclivia for TrocJiula ^ 



^ Erd- und Siisswasser-Gastropoden der Schweiz, i, pp. 143-44, 1842. 



^ Indicis Generum Malacozoorum primordia, i, p. 507. 



^ In the Manual of Conchology I raised the question whether Trochula, 

 Schl titer, 1838, type H. elegans, Gmel., should be replaced by Trochoidea, Brown, 

 111. Conch. Great Britain, 1827, monotype Trochoidea terrestre. Brown 

 (= H, elegans, Gmel.). The identity of Captain Brown's genus rests upon his 

 figures, which seem to me unmistakable, and in no way upon the identification 

 of Trochus terrestris. Pennant, as Gude and Woodward seem to infer. I did 

 not have the 1827 edition of Brown at the time I was concerned with the 

 matter, nearly 30 years ago. If there is any reason for rejecting Brown's name, 

 I would be interested to see it brought out. 



