516 



MICHIGAN SURVEY. 1905. 



VERTIGO OVATA Say. 



Shell ovate-conic, ventricose, dark am- 

 ber-colored, smooth, shining; whorls 5, 

 diminishing rapidly to a somewhat acute 

 apex, the last very much inflated, with an 

 indentation toward the aperture; suture 

 deep; peristome thin, somewhat ex- 

 panded, with a groove behind and thick- 

 ened within, aperture semi-circular, outer 

 lip strongly incurved in the centre; la- 

 mellae 6-12, 2-3 on the parietal margin, 

 Fig. 148. N. ovnta. (Morse.) two ou the Columella, 2-6 on, the peris- 



tome; umbilicus open. 

 Alt. 2, diam. 1 mm. 



Vertigo ovata, Say, Jour. A. N. S. P., II., 375, (1822). 



, W. G. Binney, Man. Am. Land Shells, 333, fig. 362, (1885). 



Pupa , Sager, Doc. H. Rep. Mich., 1839, 420, separate 14. 



Vertigo , Miles, Rep. Geol. Surv. Mich., 236, (1861). 



, DeCamp, Shell-bearing Moll. Mich., 7, (1881). 



, Walker, Rev. Moll. Fauna Mich., 17, (1894). 



The most common species of the genus and of general distribution over 

 the entire state. Distinguished from V. morsei by its ventricose last whorl 

 and conical spire, and from the other species of the genus by its larger size 

 and usually greater number of apertural lamellae. 



4 VERTIGO MORSEI Sterki. 



Shell cylindrical, turriculate, apex rather acute, imper- 

 forate, dark brown, wdth a few obsolete lines of growth, 

 whorls six, rather slowly and regularly increasing, the last 

 scarcely higher than the penultimate and rather narrow, 

 somewhat sloping toward the base; suture deep; aperture 

 comparatively small, well rounded, thickened within; peris- 

 tome everted, strongly indented on the outer wall, a moderate 

 crest behind the aperture ; a deep and large impression on the 

 body whorl over the palatal folds, and in front of it an im- 

 pression corresponding with the impression at the auricle; 

 Fi 149 apertural lamellae typically nine; three on the parietal wall; 

 V. morsei. xi3. two on the Columella, the columellar strong, with the tip 

 abruptly bent upwards, the subcolumellar horizontal, lamelliform, thin, 

 high and directed obliquely upward; basal small, sometimes double, rarely 

 wanting; palatals high and rather long, curved and directed upward, supra- 

 palatal small, nodule-Hke. 



Alt. 2.7, diam. 1.3; apert. alt. 0.9, lat. 0.8 mm. 

 Vertigo morsei, Sterki, Naut. VIII., 89, (1894). 



, Walker, Rev. Moll. Fauna Mich., 17, (1894). 



The types of this species were discovered by the late Dr. W. H. DeCamp 

 at Dewey's mill near Grand Rapids. Also found in Eaton and Washtenaw 

 counties. It has been found in the post-glacial deposits in Bay and Wash- 

 tenaw counties. 



Easily distinguished from V. ovata, which is the only species with which 

 it is likely to be confounded by its greater size, cylindrical shape and pe- 

 culiar columellar lamella. 



