478 MICHIGAN SURVEY, 1905. 



Helix hammonis, Strom, Tronclh. Selsk, Skrift, III., 425, pi. IV., fig. 16, 



(1765). 

 Zonites viridulus, W. G. Binney, Man. Am. Land Shells, 64, fig. 21, (1885). 

 Helix electrina, Miles, Rep. Geol. Surv. Mich., 235, (1861). 



Hyalina , Currier, Shell-bearing Moll. Mich., 4, (1868). 



. DeCamp, Shell-bearing Moll. Mich., 5, (1881). 



Zonites radiatulus,^2i\\iQi', Rev. Moll. Fauna Mich., 16, (1894). 



Common and of general distribution, although not as abundant as its 

 associated species, Z. arhorea. The identity of the American species with 

 that described by Strom has been only recently established, and it has been 

 usually known of V. electrina (Gld.), viridula (Mke)., or radiatula (Aid.). 



Carefvil attention is required to distinguish this species from three others, 

 which are of about the same size and same general appearance, viz.: V. 

 indentata, V. wheatleyi and Z. arhorea. But when once recognized, the dif- 

 ference between them will be found to be constant and well marked. 



V. hammonis is characterized by its more pointed spire, slightly impressed 

 suture, rapidly enlarging body whorl and narrow umbilicus, perfectly smooth 

 surface with neither radiating nor revolving, impressed lines. V. indentata is 

 imperforate and has distant, impressed radiating lines which are quite dis- 

 tinct from the growth-lines. It is also lighter colored. 



In V. wheatleyi, the umbilicus is wider and rapidly increases in size to- 

 ward the* aperture, which gives it an irregular shape; the base is somewhat 

 flattened; the aperture is more transverse, and the last whorl is slightly 

 descending at the aperture. Surface with microscopic revolving, impressed 

 lines. 



Zonitoides arhorea differs in the wider umbilicus, more depressed spire, 

 and its regularly increasing, more numerous, and more convex whorls, which 

 are separated by a well marked suture. Surface with very fine, impressed, 

 revolving lines. 



VITREA WHEATLEYI (Bland). 



Shell umbilicated, depressed, thin, shining, pellucid; brownish 

 horn-colored, finely striated, striffi decussated by very minute 

 spiral lines ; spire subplanulate ; suture slightly impressed ; whorls 

 convex, the last more convex at the base, rapidly increasing, at 

 the aperture scarcely descending; umbilicus pervious, rapidly 

 widening toward the aperture; aperture depressed, obliquely 

 lunate; peristome simple, acute, the margins approximating 

 Fip. 48. joined by a thin callus. 

 V wheatleyi. Alt. 2, greater diam. 5, lesser Zh mm. 



(Binnev.) ' 



Zonites wheatleyi, Bland, Ann. N. Y. Acad. N. S., II., 368, fig. 1, (1883). 



, W. G. Binney, Man. Am. Land Shells, 222, fig. 237, (1885). 



Helix limatula, Miles, Rep. Geol. Surv. Mich., 235, (1861). 



This species has only been recently recognized as a member of our fauna. 

 It has been found in Tuscola, Kalamazoo, Kent, Benzie and Grand Traverse 

 counties, which indicate a general distribution in the northern and western 

 portion of the lower peninsula. 



It is pecuhar in the oval shape of the umbilicus, resulting from the rapid 

 increase in the size of the body whorl during the last half of its growth. 



