86 EOCENE MOLLUSCA. 



Limnea longiscata. Lyell and Murch. 1829. Mem. sur les depots lacustres tert. du 



Cantal. 

 Limnea — Bouill. 1836. Cat. des coq. foss., &c, p. 157, No. 6. 



— — Gratel. 1838. Cat. des debris foss., &c, du Bassin de la Gironde, 



p. 33, No. 100. 

 Lymn,ea — Desk. 1838. Lam. Hist. Nat. &c, 2d edit., vol. viii, p. 422, No. 7. 



L. testa lavi, elongatd, sub-turritd, acuminata: anfractibus sex aut septem, convexius- 

 culis ; suluris sub-depressis : aperturd ovato-acutd, antice dilatatd, spirant in longitudinem 

 vix cequanti ; labro parum expanso ; columella marginatd ; plica columellari lata, compressd, 

 parum eminenti, bipartitd. 



Var. distorta; testa longiori, angustiori, anfractibus pirn decurrentibus ; aperturd 

 breviori. 



This Limnsea is more abundant, and, although it presents many varieties of form, is, 

 perhaps, better characterised than any other fossil species. It is a smooth, elongated, 

 narrow, subturrited shell, composed of seven or eight convex whorls, somewhat 

 depressed at the suture. The aperture is oval, rather effuse in front, and, in the 

 typical form, is a little shorter than the spire ; the inner lip is thick, but does not 

 extend much beyond the aperture. The columellar fold is broad, flat, not very 

 prominent, and widely but not deeply sulcated. 



A variety frequently occurs (fig. 3 e — h), in which the line of the suture runs below 

 the wide part of the whorl, giving an irregular distorted appearance to the shell, and 

 shortening the aperture, the length of which barely equals two fifths of the whole 

 shell. 



Although there can be but little doubt that this is the true Lymnee effilee of Brard, 

 the columellar fold does not correspond with the description given by M. Deshayes, 

 in which it is represented to be small and rounded ; but in the few French specimens 

 which I have had an opportunity of examining, the columellar fold corresponds with 

 that of the English specimens. I presume, therefore, that the form described by 

 M. Deshayes was a modification of the more general form. 



The shell figured and described by Brard as L. pyra?nidalis, appears to me, as 

 I have already stated, from its elongated narrow shape, the form of the aperture, 

 and the slight elevation of the fold, to be merely an adult specimen of this species — 

 similar to that represented by fig. 3 c and d. The " double suture," or " narrow 

 spiral riband," running along the edge of the suture, which Brard mentions as 

 distinguishing L. pgramidalis, frequently occurs in this, as well as in other species ; 

 it is not, however, a constant character in any, and cannot be relied upon as a specific 

 distinction. 



A form occurs, rather plentifully, in Hordwell Cliff, which Mr. Wood (' Lond. 

 Geol. Journ.' vol. i, p. 118,) has referred to L. strigosa, (Brogn.) That species, 

 apparently, was proposed from casts or mutilated specimens, and is a questionable 



