8o LAND AND FRESH WATER MOLLUSKS 



whorl subcompressed laterally ; aperture elongate-ovate, about 2f times 

 its length being equal to the length of the shell ; margin thickened, and 

 continuous over the body, reflected over an umbilical chink behind the 

 pillar but not quite closing it ; pillar vs^ith a marked fold ; surface with 

 close-set fine axial elevated lines in harmony with the lines of growth, 

 and crossed by microscopic revolving striae which sagrinate the surface ; 

 there are also malleations, obscure sparse revolving ridges, etc., on in- 

 dividual specimens. Length of shell 19; aperture 7.0; max. diam. 

 7.0, of aperture 4.5 mm. 



Range. — Pleistocene marl of Marl Lake, Anticosti Island (Sir 

 William Logan and Dr. J. Schmitt). Recent? 



This interesting species resembles somewhat X. desidiosa^ to which 

 it has usually been referred, but it has two more whorls and a more 

 slender and elevated spire, and in most specimens a more parallel -sided 

 aperture. I am unable to say whether it occurs in the recent state, but 

 the numerous specimens I have seen are all fossils. Dr. Lea had 

 labelled his specimens 'Z.. acuta Lea,' doubtless forgetting his own 

 species of the same name, which is a very different shell. 



Uncertain Species. 

 There are several nude names in the literature which cannot be iden- 

 tified and yet may puzzle the student who is unaware that they have 

 not been described. Of such are L.fossaria J. de C. Sowerby (1836) , 

 in Richardson's Fauna Boreali Americana ; L. petitii'B&ck (1838), 

 listed from Newfoundland in his ' Index ' ; and X. opacina Bell (1858), 

 listed in the Annual Report of the Canadian Geological Survey. 



Genus Planorbis Miiller. 



Planorbis Petiver, Gazophyl. Nat. et Artis Dec, p. 16, tab. 10, fig. 11, 1702 

 (not binomial). The species figured is Helix planorbis Linne, Fauna 

 Suecica, p. 527, 1761. — Guettard, Mem. Acad. Roy. des. Sci. (1756), 

 p. 151, 1 762 (not binomial), first sp. Plan, brun., after Lister, Anim. Angl., 

 p. 143, pi. II, fig. 26 (= Helix corneus Linne). — Geoffroy, Traite Som. 

 des Coq. Fluv. Paris, pp. 81, 84, 1767 (not binomial), § i, Helix cornea 

 Linne ; Ibid., translation by Martini, Niirnberg, pp. 10, 75, 1767. 



G7r^/«^ Adanson, Hist. S6n6gal, p. 7, 1757 (not binomial), sp. figured re- 

 sembles P. parvus Say. 



< Planorbis Muller, Verm. Terr., 11, p. 152, 1774, no type selected ; Prodr. 

 Zool. Dan., pp. xxx, 238, 1775. — BRUGUifeRE, Enc. Meth., i, p. xvi, 

 1789, nude name. — Bolten, Mus. Bolt., p. 51, 1798. — Lamarck, Pro- 

 drome, p. 76, 1799 ; Syst. des An. s. Vert., p. 93, 1801. — Draparnaud, 

 Tabl. Coq. Terr, et Fluv., pp. 30, 42, 1 801.— Schumacher, Essai, p. 

 255, 1817 ; not of Perry, 181 1. 



=-Planorbis Montfort, Conch. Syst., ll, p. 270, 1810, selects as type P. 

 corneus L. 



