I06 LAND AND FRESH WATER MOLLUSKS 



Later on Herrmannsen supplies a gratuitous derivation for Fleming's 

 name and, because it does not properly conform to his imaginary 

 source, alters the spelling to Aplecta. 



This was totally unauthorized. Since no derivation w^as given by 

 Sov^erby, w^e are at liberty to regard the word as an arbitrary combi- 

 nation of letters formed on the analogy of triplex and similar Latin 

 words, but we are not at liberty to manufacture an imaginary deriva- 

 tion and then force the name to conform to it. 



Several authors divided Miiller's group differently, and several syn- 

 onyms were proposed for parts of it, as will be evident on a study of 

 the synonymy. 



The genus occurs in the Tertiary of Europe and North America, 

 and possibly as far back as the Middle Cretaceous of North America. 

 Several well characterized forms have been described from the Lara- 

 mie. The type is known from the Palearctic and Nearctic regions, 

 and the genus extends south to Mexico, where in the tropical condi- 

 tions of Mazatlan perhaps the finest of the recent species occurs abun- 

 dantly. In Alaska and on the adjacent continent of Asia but one 

 species is known, the type. 



Aplexa hypnorum (Linn6). 



Bulla hypnorum Linne, Fauna Suecica, ed. i, No. 1303, 1746; ed. il, No. 



2159, p. 522, 1761 ; Syst. Nat , ed. x, p. 727, 1758 ; ed. xii, p. 1185, 



1767. 

 Bulimus hypnorum Bruguie;re, Encycl. Meth., p. 301, 1792. 

 Planorbis turritus Muller, Verm. Terr., 11, p. 169, 1774. 

 Physa hypnorum Draparnaud, Hist., p. 55, pi. iii, figs. 12-13, 1805. — 



Haldeman, Mon. Limn., p. 36, pi. v, figs. 4-9, 1842. — Forbes and 



Hanley, Brit. Moll.,- iv, p. 143, pi. cxxii, figs. 6-7. 

 Bulla hypnorum Montagu, Test. Brit., ii, p. 228, 1803. 

 Bulla turrita Gmelin, Syst. Nat., vi, p. 3428, No. 20, 1792. 

 Aplexa hypnorum Sowerby, Genera, fasc. vii, 1822. — Fleming, Hist. Brit. 



An., p. 276, 1828 ; Encycl. Brit., ed. vii, 1837 ; Art. MoUusca, reprinted 



as • Molluscous Animals, ' 8°, Edinburgh, p. 158, 1837. 

 Turbo stagnalis W xi.v.^K, Test. Min. Rar., p. 15, pi. 11, fig. 54, ^7^7- 

 Nauta hypnorum (Leach, in) Turton, Man., p. 129, 183 1. — Leach, Syn. 



Moll. Gt. Brit., p. no, 1852. 

 Physa hypnorum. Hist, des Moll., p. 55, pi. in, figs. 12, 13, 1805. — Pfeiffer, 



Naturg. Deutscher Land. Moll., i, p. 97, 1821. 

 Bullinus turritus OviK^, Lehrb. d. Naturg., p. 303, 181 5. 

 Physa hypnorum Lamarck, Anim. s. Vert., vi, Pt. 11, p. 157, 1822. 

 Physa elongata Say, Journ. Acad. Nat. Sci. Phila., il, p. 171, 182 1. — Gould, 



Inv. Mass., p. 214, fig. 143, 1841. — De Kay, Zool. N. Y. Moll., p. 81, 



pi. VI, fig. 346, 1843. 

 Physa turrita J. de C. Sowerby, in Richardson, Fauna Bor. Am., iii, p. 315, 



1836. 

 Physa glabra De Kay, Zool. N. Y., Moll., p. 80, pi. v, fig. 83, 1843. 



