182 The Molluscan Family Planorhidae 



Species Considered as Valid. Five species, in one of which two races 

 are recognized, are attributable to Promenetus. 

 Promenetus exacuous exacuous (Say) Promenetus rubeUus (Sterki) 



Promenetus exacuous Jtiegas (Dall) Promenetus hudsonicus (Pilsbry) 



Promenetus umbilicatellus (Cockerell) Promenetus imus (Vanatta) 



Geological Distribution. Pliocene to Recent fauna. 



Remarks. Promenetus, first described as a group of the genus Menetus, 

 differs so radically from Menetus in the form of the penial gland that 

 it is deemed necessary to raise the group to generic rank. Its gland 

 resembles Planorbula in the lack of a distinct duct and in the opening of 

 the gland which is lengthwise instead of at the end of a cylindrical sac-like 

 gland, as in typical Menetus and its subgenus Micromenetus. The form of 

 the penial complex is also more like that of Planorbula than like this organ 

 in Menetus. In other respects, the genus Promenetus conforms to the gen- 

 eral characteristics of the subfamily. 



The discovery that the species long known as Gyraulus umbilicatellus 

 is a Menetus closely related to exaciious (Baker, 1935, p. 46) was a surprise 

 and shows that the group Promenetus includes species with both rounded 

 and sharply carinated whorls. The vas deferens in typical Menetus enlarges 

 as it enters the vergic sac to fprm an einphallus. In Promenetus and 

 Planorbula, there is no such enlargement. 



Genus MENETUS H. and A. Adams, 1855 

 Type designated by D.\ll in 1870, Planorbis opercularis Gould 



1855. Menetus H. and A. Adams, Genera of Rec. Moll., II, p. 262. Includes several 

 unrelated species among which is Planorbis opercularis Gould. (Non Menetus 

 of Chenu, 1869, P. Fischer, 1883, Tryon, 1884, C. A. Westerlund, 1885, or von 

 Martens, 1899) 



1865. Menetus W. G. Bixney, L. and FW. Sh. N. A., II, p. 125. No type cited but 

 includes Planorbis opercularis and P. exacuous {== exacutus) . As subgenus of 

 Planorbis 



1870. Menetus Tryon, Con. Haid. Mon., pp. 188, 206. Xo type cited but inckides 



both Planorbis opercularis and P. exacutus. As subgenus 

 1870. Me7ietus D.\ll, Ann. N. Y. Lye. N. H., IX, p. 351. Type designation, Planorbis 



opercularis Gould. As subgenus 

 1886. Menetus Clessix, Syst. Conch. Cab., XVII, p. 33. Type Planorbis opercularis 



Gould. As genus 

 1905. Menetus D.^ll. Alaska Moll., pp. 82. 86. Type Planorbis opercularis Gould. 



Section of subgenus Hippeutis Agassiz 

 1918. Menetus Walker, Miscel. Pub. Mus. ZooL, Univ. Mich., Xo. 6, pp. 12, 94. Type 



Planorbis opercularis Gould. Section of subgenus Hippeutis Agassiz 

 1923. Menetus Wenz, Fossil. Cat.. Pars 22, p. 1650. Genotype Hippeutis (Menetus) 



opercularis (Gould). Few of the .species listed are true members of the genus 



Menetus, which is not found in Europe. They might belong in the genus 



Anisus. Subgenus of genus Hippeutis 

 1923. Menetus Germ.mx, Rec. Ind. Mus., XXI, pp. 8, 156. Tvpe Planorbis opercularis 



Gould. As subgenus of Planorbis 

 1926. Menetus F. C. Baker, Trans. Wis. Acad. Sci., Arts and Lett., XXII, p. 203. 



T3'pe Planorbis opercularis Gould. Anatomy. As genus 



1928. Menetus F. C. Baker, Fresh-water Moll. Wis., I, p. 360. Type Planorbis oper- 



cularis Gould. Anatomy. As genus 



1929. Menetus J. Henderson, Univ. Col. Studies, XVH, No. 2, pp. 140-141. As sub- 



genus of Planorbis 



