96 The MoUuscan Family Planorhidae 



ing more like some of the species of Planorbis or Anisus. IVIany of the 

 names of groups of the Planorbidae have been used rather loosely by 

 European writers. Sandberger, for example, lists the subgenera Menetus, 

 Helisoma, and Carinifex among the European fossils, groups which we now 

 know are confined to America and have no representatives outside the 

 Western Hemisphere. All of the extinct Planorbidae, both American and 

 European, are badly in need of a thorough taxonomic revision. 



Species Considered as Valid. Anisopsis calculus (Sandberger). the 

 genotype, is the only sj^ccies unciucstionably assigned here. The assignment 

 of Planorbis loryi Cociuand seems indefensible. 



Subfamily SEGMEXTININAE F. C. Baker, New 



The prostate diverticula are simple sacs placed in a single row along a 

 prostate duct as in the subfamily Planorbinae. The penial complex has 

 one or two flagella placed at the end of the vergic sac and in addition sev- 

 eral genera have a penial gland in the preputium. The jaw is fragmented 

 as in Planorbinae. The radula teeth are modified by additional cusps or 

 by the presence of many interstitial cusps. The kidney is without a ridge. 



Type genus Segmentina Fleming. 



The groups included in this subfamily are as follows: 



With penial gland but without duct: Segmentina, Hippeutis, Pingiella. 

 With penial gland and an external duct: Intha. 

 Without penial gland: Polypylis, Drepnnotrema, Acrorbis. 

 With long flagella: Pingiella, Polypylis, Intha. 

 With short flagella: Scgme7itina, Hippeutis, Acrorbis. 

 With both long and short flagella: Drepanotrema. 



With lamellae or barriers within the aperture: Segmentina, Polypylis, Trochorbis. 

 Without lamellae or barriers within the aperture: Hippeutis, Helicorbis, Pingia, 

 Intha, Drepanotrema, Platytajyhiu.-^. Acrorbis. 



Several groups have not been examined anatomically and their position 

 is doubtful. Such are Helicorbis, Trochorbis, and Platijtophius. The fossil 

 group Paraplatiorbis must, of course, be placed by shell characters alone. 



Genus SEGMENTINA Fleming, 1817 

 Monotype Xautilus lacustris Lightioot ^^ Planorbis nitidus O. F. Miiller 



1817. Segmentina Fleming, Edinburgh Encyclopedia. Conchology, ed. VII, Vol. XII. 



Monotype, Nautilus lacustris Lightfoot = Planorbis nitidus O. F. Miiller 



1818. Segmentina Fleming, Supplement to 4-6th ed. Encyc. Brit., Ill, 'Conchology,' 



p. 309. Type Nautilus lacustris Lightfoot 



1819. Hemithalamus Le.ach, Moll. Brit. Synop. (proofs), p. 137 



1831. Hemithalamus 'Leach' Turton, Man. Land Fresh-water Shells Brit. Isl., p. 116. 

 In synonymy of Segmeyitina nitida 0. F. Miiller 



1833. Hemithalamus Fitzinger, Syst. Verz, p. 110 



1840. Segmentaria Sw.\inson, Treat. Malac, p. 337. Lapsus for Segmentina. As sub- 

 genus of Planorbis 



1842. Segmentina H.'\ldem.\n, Mon. Fresh-water Univ. Moll., U. S., p. 14. No type 

 cited. As subgenus of Planorbis 



1847. Segmentina Gr.ay. Proc. Zool. Soc, p. 509. Type Nautilus lacustris Lightfoot. 

 As genus 



1847. Discus Gray, Proc. Zool. Soc, p. 509. No type cited. As synonym of Seg- 

 7)ienti7ia 



1850. Segmentina (part) Stein, Schnecken u. Musch. Berlins, p. 78. Segmentina x 

 Hippeutis 



A 



