THE NAUTILUS. 

 NEW AMERICAN LYMNAEAS. II. 



BY FRANK COLLINS BAKER. 



Lymnsea decollate! oronoensis var. nov. 



Shell very globose, inflated, solid ; whorls 3-3^, very convex, the 

 last almost globular ; spire broadly conic, depressed, sutures a little 

 impressed ; aperture roundly ovate, the upper part shouldered two- 

 thirds the length the entire shell ; columella with a distinct plait ; 

 umbilicus very narrowly open ; color a rich greenish horn, inclining 

 to black in some specimens. The spire is frequently decollated. 



width 11.50; aperture 

 width 10.00 ; aperture 



length 11.00 



width 7.00 



length 



10.00 ; width 6.00 



width 12.00; aperture length 12.00; width 8.00 



length 



8.75 ; width 5.50 



Length 17.00 

 mill. 



Length 16.00 ; 

 mill. 



Length 17.00 ; 

 mill. 



Length 12.00; width 9.00; aperture 

 mill, (half grown). 



Distribution: Orono, Maine. (Collection of Mr. Bryant Walker.) 



This variety may be distinguished from decollata by its larger 

 size, more globose form of whorls and the whole shell, and the 

 rounded aperture shouldered at the upper part. The young or half- 

 grown shell somewhat resembles young individuals of mighelsi and 

 catascopium. 



Haldeman's figure 3 on plate 14 of his monograph seems to repre- 

 sent a form of this variety. It appears to be quite a characteristic 

 variety. 



Judging from specimens received by Mr. Bryant Walker from 

 Mighels and examined by the writer, decollata has been figured 

 accurately only by Haldeman in his monograph, plate 14, figs. 1, 2. 

 The species has not been understood by most American collectors, 

 specimens of einaryinata, catascopium and migltehi having been re- 

 ceived as decollata. It is, however, a very characteristic species, 

 not closely connected with any other form. The variety oronoensis 

 resembles some young forms of mighelsi as well as some varieties of 

 catascopium. This resemblance, however, is merely superficial. 



The typical decollata received from Mighels measure as follows : 



Length 12.00 ; width 8.00 ; aperture length 9.00 ; width 5.50 milL 



