168 PKOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Genera, Gi/rotoma, s.s., Pleurocera, svib-gen. lo. 



Througli the efforts of E,afinesque, Lea, Haldeinan, Anthony, and 

 the Adams during tlie early and middle parts of the hist century the 

 classification of tliis family has been so burdened with unreduced 

 specific synonyms and a sujierabundance of genera that no subsequent 

 writer has cared to undertake its thorough revision, while but two, 

 Tryon ^ and Pilsbry,- have given serious attention to the group since 

 that time. 



In an endeavour to straighten out the involved generic nomenclature 

 of the Western forms the recent members of the entire family have 

 been reviewed, and from among the hundreds of nominal species nine 

 -species and four sub-species, representing three genera, have been 

 selected as entitled to serious consideration.^ 



It is not anticipated that this treatment will meet with general 

 approval in every instance. In the absence of a field acquaintance 

 with the species from east of the. Rocky Mountains (the family is 

 restricted to the Nearctic Region, and chiefly to the Mississippi Vallej'), 

 and the necessity of depending on figures, locotypes, and named 

 specimens, certain errors are bound to creep in. If, however, the 

 way is paved for a thorough revision, the mission of these pages will 

 have been fulfilled. To assist in this types have been cited for 

 all the group names current in the literature, without, however, 



' Strepomatidse, Smith. Misc. Coll., No. 253, 1873. 



- In Pilsbry & Rhodes, Proc. Phikd. Acad. Nat. Sci., 1896, pp. 495 ff. 



■' The genus Ellipstoiiia ( + Anculosa, Say), ordinarily included in this family, 

 in reality groups by itself in the Ellipstomidfe, nov. The species (if there 

 is more than one with several sub-sj)ecies) are wholly confined to the 

 waters east of the Mississippi River, and hardly concern us here. The 

 following is a summary of the generic arrangement : — 



Genus Ellipstoma, Rafinesque. 

 Kllipstoma, Rafinesque, 1818 (-E. gibbosa, Raf.) ; Lithasia, Haldeman, 1840- 

 {Anculosa {Lithasia) genicula, Hald. = E. gibbosa, Raf.). 

 Type, Ellipstoma gibbosa, Rafinesque. 



Sub-genus Anculosa, Say. 

 Leptoxis, Rafinesque, 1818 (no species cited, description apparently based on 

 prcerosa) ; Anculosa, Say, 1821 {Melania {Anculosa) prcerosa, Say) ; 

 Anculotus, Say, 1825 (emended form) ; Leptoxis, 'Rafinesque,' Haldeman, 

 1847 {L. rctusa, Raf . = ? A. prcerosa. Say); Eurycalmi, Lea, 1864 

 {Goniobasis {Eitrycalon) umbonatian. Lea = A. pnvrosa, Say). 

 Type, Melania {Anculosa) prcerosa. Say. 



Sub-genus Mudalia, Haldeman. 



Didimus (sp.), Bruguiere, 1792 {B. carinatus, Brug.) ; Paludina (sp.). Say. 

 1819 (P. dissimilis, Say = B. carinatus, Brug.) ; Mudalia, Haldeman, 

 1840 (P. dissimilis. Say = B. carinatus, Brug.) ; Nitocris, H. c& A. Adams, 

 1854 {Anculosa carinata. Lea = B. carinatus, Brug., first species) ; 

 Spirodon, ' Anthony MS.,' Tryon, 1873 {A. monodontoiclcs, Conr. = B. cari- 

 natus, Brug.), in synonymy. 

 Type, Bulimus carinatus, Bruguiere. 



The genetic relations of these three are in reverse order. Mudalia represents 

 the most primitive, and Ellipstoma the most highly modified stage. 



