LIJIN^A. 473 



nal of the Acadoni)' of Natural Sciences," ii. 167, as " L. columella, 

 var. a. small, black, from Cold Water Creek, Missouri." 



The form called Limncca macrostoma is thus described in the 

 first edition. Fig. 148 : — 



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 shin- 

 ing, 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 ma- 

 ture, broadly expanded; outer lip very sharp and thin, L.macros. 



.„ -. .,...,1 T toma. 



broadly rounded \\\ front, and mamtammg 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 en- 

 croaches upon the aperture. Length, eleven twentieths of an inch ; 

 breadth, seven twentieths of an inch ; divergence, seventy-three 

 degrees. 



Found at New Bedford l)y Mr. Shiverick. Much larger speci- 

 mens were obtained by Colonel Totten, at Tiverton, Rhode Island. 

 Dr. Binncy 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 that shell is much 

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

 being not more than sixty degrees. Such specimens Professor 

 Adams described as his L. acuminata. But at maturity the shell 

 is very distinctly characterized by its widely s])reading outer lip, 

 which gives great expansion to the aperture. jMr. Say received it 

 from the rice-fields of Carolina. It is the analogue of the L. ovata 

 of Europe. 



Limnsea decoUata. 



Shell ventricose, rather thick, olivaceous-green color; whorls two to three, 

 body whorl composes almost the whole shell ; aperture very large, sub-campanu- 

 late ; columella-fold very prominent. 



Limmm drcoUata, Mighels, Troc. Bost. Soo. i. 49 (1841) ; Bost. Joiirn. iv. 4-5, 336, pi. 

 4, fifr. 13 (and Adams) (1842). — W. G. Binney, Smith. Inst. L. and Fr. W. Shells, 

 ii. 31, fi-s. 36, 37 (1865). 



