OF NORTH AMERICA. 313 



to be confined to any particular locality, but is found in any consider- 

 able lot of shells from any locality. (See the figures on the plates.) 

 It is evident from a study of the figures of palustris in European 

 works (Forbes and Hanley, Sowerby, Martini and Chemnitz, etc.) 

 that the large, rather corpulent form is to be considered as typical. 

 This form is absolutely identical with American specimens, series from 

 both continents being indistinguishable when mixed. There are, how- 

 ever, several varieties or races which seem recognizable. Very distinct 

 variations are frequently seen in shells from different parts of the 

 same body of water, as notably illustrated by the palustris in Owasco 

 Lake, N. Y., where specimens from the west shore are very large and 

 thin (pi. XXXIII, figs. 2-7) while those from the north end are smaller 

 and very solid, in some individuals recalling both Galba catascopium 

 and Galba palustris desidiosa (PL XXXIII, figs. 8-10). 



A study of the types of Lea's Lymnaeas in the Smithsonian Insti- 

 tution conclusively proves that nuttalliana (pi. XXXIII, figs. 22-23) 

 and haydcni (pi. XXXIII, fig. 25) are absolute synonyms of palus- 

 tris, haydeni being a slight modification of the nuttalliana form. The 

 characteristics of a corpulent shell or a strongly plicate columella are 

 of no consequence whatever when a series is examined, such as is 

 shown on plate XXVI, where figs. 20 and 17 seem very distinct when 

 placed side by side, but are seen to be easily and gradually connected 

 with each other in a large series. (Compare also fig. 21 with fig. 26.) 

 These mutations are very interesting, but are not of taxonomic im- 

 portance, being simply individual variations. Lymnaa e.vpansa Hald. 

 is a form in which the outer lip is expanded; the same is true of suf- 

 flatus Calkins. Plcbcia Gould, a nude name, is an absolute synonym 

 of palustris. Limn&us sordidus Kuster, is a synonym of palustris, 

 judging by Von Martens' references to Haldeman, plate 6, figure 1. 

 The locality "Central America" is an error as no member of the palus- 

 tris group (except attenuata) is found south of the Rio Grande. It 

 is probably a case of mixing labels. Specimens in Bunker's collec- 

 tion, now in Berlin, are said by Von Martens to be like Haldeman's 

 figure 5 on plate 7. These are marked "Central America." 



Unlike the Lymnaeas previously considered (excepting caperata) 

 palustris forms several distinct ribs or rest varices in its shell, as many 

 as four being distinctly seen in some specimens, although three seem 

 to be the normal number. In the majority of specimens one varix is 

 formed on the third whorl, one on the fifth whorl and one on the 

 margin of the aperture. Whether these varices are formed yearly or 

 simply mark periods of hibernation when the animal is buried in the 



