HANNIBAL: CALIFORNIAN FRESHWATER MOLLTJSCA. 143 



Likewise a decidedly primitive species; the differential character 

 between these two and L. stagnalis is, however, rather one of degree 

 than any tangible distinction. 



Ltmn^a megasoma (Say). 

 Lymneus megasomtis, Say, 1824. 



Shell very large, solid, bulimuliform, spire elevated, whorls inflated, 

 imperforate, aperture sub-auriculiform, columellar fold well developed 

 or sub-obsolete ; habitat lakes and sluggish streams. 



Hudson Bay and St. Lawrence drainages, American Province. 



A fine large species, which at first glance would hardly seem 

 referable to the same genus as Lymneus atagnalis, but connected 

 with it by L. paliistris and similar forms ; in essential particulars it 

 is a true Lymncea. The colouring is unusually pronounced, but 

 L. reflexa, likewise a heavy-shelled species, presents much of the 

 same thing. 



Ltmn^a Coktracosta, J. G. Cooper. 



Limnea Contracosta, J. G. Cooper, 1894. 



Shell of moderate size, spire acutely elevated, whoi'ls elongate, 

 rather appressed, and imperforate, aperture succiniform, columellar 

 fold well developed ; habitat apparently lacustrine. 



Miocene : Contra Costa Lake beds, California ; Mascall Lake beds, 

 Oregon. 



A species suggesting Z. columella, but more attenuate, and nearly 

 twice the size, whorls long as in L. megasoma. The type was badly 

 crushed, hence the original figure does not portray the specific 

 characters well. The species is not imcomraon in the Miocene of 

 the Berkeley Hills, however, so that its recognition is comparatively 

 simple. 



Lymn^a Stearnsi, Hannibal. 

 Limnaa maxima, Stearns, 1902 (nude name), 1906, figure, not 

 L. stagnalis Wiv. maxima, Collins, 1872; Z. Steariisi, ^-dnmhiCi 

 in F. C. Baker, 1911 (copy of original fig. of itiaxima, Stearns). 



Shell large, spire elevated, whorls inflated and imperforate, aperture 

 sub - auriculiform, columella strongly folded ; habitat apparently 

 lacustrine. 



Miocene : Mascall Lake beds, Oregon. 



A species of the build of Z. paltistris, but decidedly larger and 

 proportionally broader. Stearns' figure is nearly half as large again 

 as the natural size and rather crude. 



Ltmn^a Cooperi, n.sp. PL YI, Figs. ISa-c. 



Limncsa '■ ohnissa. Say', Tryon, 1865 (partim) ; L. ^ lepida, Gould', 

 Carlton, 1870 ; Limnophysa ^ferniginea, Halderaan ', J. G. Cooper, 

 1870; Z. ' obrussa. Say', J". G. Cooper, 1872 {partim); Limncea 

 ' obrussa, Say (desidiosa, Say)', Wood & llaymond, 1891; 

 L. 'obrussa, Say', Hannibal, 1910. 

 Shell small for group, spire acuminate, whorls rather compressed 



and imperforate, aperture narrowly auriculiform, columellar fold 



VOL. X. — JUNE, 1912. 10 



