MESODON. 321 



Tlie specimens figured show how variable the species is in size. In color it 

 is also very variable ; sometimes it is found of a uniform red, at others albino. 



The varieties mentioned by PfeifTer and Dcshayes are distinguished merely 

 by the revolving bands. In a large suite of specimens it is rare to find two on 

 which these bands and lines are similarly arranged. Some have a parietal tooth. 



It would appear from the statement made by Dr. Kirtland that its habits are 

 somewhat peculiar. " Wet marshes arc its principal resort, where, during 

 summer, it may be seen climbing about on weeds and blades of grass, appar- 

 ently endeavoring to avoid the water collected beneath it. At the approach 

 of winter it retreats to the tops of the carex-bogs, where several dozen may be 

 found collected together in a torpid state, with the mouths of their shells closed 

 with an cpiphragm. They usually form a shallow excavation on the bog, con- 

 cealed beneath the tufts of dead grass." The numbers collected in these 

 retreats are sometimes " agglutinated into one mass." This habit of attaching 

 themselves to each other in numbers, during their hibernation, I have not wit- 

 nessed in any other of our species, but I believe it is common in some European 

 species. 



Jaw arcuate, of uniform width ; ends blunt ; anterior surface with numerous, 

 crowded ribs, denticulating either margin. 



Lingual membrane (PI. VIII. Fig. L) with 42 — 1 — 42 teeth; 17 perfect 

 laterals. 



Genitalia (see Vol. I., 1. c). Penis sac long, stout, with a very highly devel- 

 oped prepuce on the greater part of its course, then tapering to its summit, 

 where it receives the vas deferens and retractor muscle ; genital bladder long, 

 subcylindrical, its duct but slightly smaller, short, swollen at its entrance into 

 the vagina ; oviduct greatly convoluted. 



Mesodon Pennsylvanica, Green. 



Vol. III. PI. vn. 



Shell imperforate, convex, elevated ; epidermis yellowish horn-color, or rus- 

 set ; whorls 6, convex, with crowded, elevated, oblique strife ; suture distinctly 

 marked ; aperture subtriangular, contracted by the peristome ; peristome white, 

 naiTow, reflected, not flattened, with sometimes a slight thickening on the inner 

 side near the base; umbilical region indented. Greater diameter 17, lesser 

 15 mill.; height, 11 mill. 



Helix Pennsylvanica, Green, Contributions to Macl. Lye, Nos. 1, 8. — P>ixxey, 



Bost. Journ. Kat. Hist., I. 483, PI. XVL (1837) ; Terr. Moll., IT. 105, PI. 



VII. — Pfeiffer, Symbolic, II. 36 ; Mon. Hel. Viv., I. 291 (excl. H. clausa) ; 



IV. 321 ; in Chemnitz, ed. 2, II. 51, t. LXXIII. Figs. 4, 5 (excl. H. clausa). 



— DeKay, N. Y. Moll., 41, PI. III. Fig. 35 (1843), — Mrs. Gray, Fig. Moll. 



An., PI. CCXCI. Fig. 5, from Bost. Journ., no descr. — Reeve, Con. Icon., 



No. 676 (excl. syn.). — Bland, Ann. N. Y. Lye, VI. 299 (1858). — W. G. 



Binney, Terr. Moll., IV. 45 ; L. & Fr.-W. Sh., I. 140 (1869). 

 VOL. IV. 21 



