LIMNEANA. MOLLUSCA. LIMN/EA. 217 



Limn^'a macrustoma. 



Shell fragile, ovate, apex acute ; whorls four, lines of groicth 

 corrugated ; aperture four fifths the length of the shell, ample, ex- 

 panded, umbilicus minute. 



Figure 14S. 



Stale Coll., No. 13S. Soc. Cab., No. 1296. 



Lymneus macrostomus, Say ; Journ, /lead. Kat. Sc, ii. 170. 

 Limnea acuminata, Adams ; Sillimnn's Journ., xxxix. 374, (young.) 



Shell fragile, pellucid, light horn-colored, ovate-conical ; last 

 whorl very large, moderately inflated, surmounted by three very 

 small, oblique ones, forming an acute apex ; surface shining, 

 marked by fine lines of growth, which are crossed and rendered 

 flexuous by numerous revolving lines, faintly visible without a 

 magnifier ; suture distinct, the whorls approaching it by a gradual 

 slope ; aperture ovate, very ample, four-fifths the length of the 

 shell, and, when mature, broadly expanded ; outer lip very sharp 

 and thin, broadly rounded in front, and, maintaining its sharp edge, 

 it rises and disappears within the shell ; pillar so broadly arched 

 as to allow a view of much of the interior of the spire ; a minute 

 umbilicus is formed by a reflected scale of enamel ; in mature 

 shells a glazing of enamel is found upon the preceding whorl as it 

 encroaches upon the aperture. Length |i inch, breadth 2V inch, 

 divergence 73°. 



Found at New Bedford by Mr. Shiverick. Much larger speci- 

 mens were obtained by Colonel Totten, at Tiverton, Rhode 

 Island. Dr. Binney found it also in Vermont. 



This shell is closely allied to L. columella, and in an immature 

 state is not easily distinguished from it ; but tliat shell is much 

 more elongated, and regularly tapering, the divergence of the spire 

 being not more than 60°. Such specimens Professor Adams described 

 as his L. acuminata. But at maturity the shell is very distinct]}'- char- 

 acterized by its widely spreading outer lip, which gives great expan- 

 sion to the aperture. Mr. Say received it from the rice-fields of Car- 

 oUna. It is the analogue of the L. ovatus, of Europe. 

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