18 THE NAUTILUS. 



Lymnsea liakeri n. sp. PI. II, figs. 11-12. 



Shell slender, elongate, perforate ; whorls 5 ; spire elongated, tur- 

 reted ; apex acute ; body whorl narrow, elongated, compressed below ; 

 suture deeply impressed ; lines of growth fine and regular with fine 

 subobsolete, revolving, spiral lines ; aperture narrow, elongated, within 

 the flare of the lip, the sides are nearly parallel, and about equally 

 rounded above and below ; lip thin, sharp, suddenly and broadly 

 expanded, subreflected, continuous, not appressed to the parietal wall, 

 and roundly reflected over the perforation, columella straight, with- 

 out a fold ; axis round and smooth. 



Alt. (fig. 12) 16.5, diam. 7.5, length ap, 8.5, width 4.5 mm. 



Types (No. 9353 Coll. Walker) from Pine Lake, Charlevoix 

 County, Mich. 



This remarkable species was dredged from the marl bottom of 

 Pine Lake. No living specimens were found, and in all prob- 

 ability it is extinct. In its external characteristics it is more 

 nearly related to L.jayi Dunker (gracilis Jay) than to any other of 

 the described species, but the resemblance is a general one only, the 

 two species differing in nearly every detail. The continuous, free lip 

 and straight columella are exceedingly like those of jayi, and would 

 naturally cause it to be referred to the subgenus Acella. But the 

 axis is not gyrate, as in that group, but is rounded and without a 

 fold, as in Galba. 



The young shell (fig. 11) is subcylindrical, and with its heavily- 

 shouldered, turreted whorls and narrow aperture reminds one of the 

 curious L. contracta Currier from Houghton Lake. I take pleasure 

 in dedicating this very peculiar species to Mr. Frank C. Baker, of 

 the Chicago Academy of Sciences, who has made a special study of 

 the North American Lymnceas. 



EXPLANATION OF PLATES. 



PLATE I. 



Figures 1-4 inclusive are enlarged. The remainder are of natural 

 size. 



Fig. 1. L. emarginata Say (immature), Isle Royal, Mich. 



Figs. 2, 9 and 10. L. pilsbryana Walker (immature), Isle Royal, 

 Mich. 



Fig. 3. L. petoskeyensis Walker, Petoskey, Mich. 



Fig. 4. L. desidiosa Say, Ann Arbor, Mich. 



