MOLLUSCA OF MICHIGAN— WALKER. 



517 



Fig. 150. 



Isthmia 

 Vertigo 



VERTIGO VENTRICOSA (Morse). 



Shell umbilicate, ovate-conic, smooth, polished, 

 whorls 4, convex; suture deeply impressed; aper- 

 ture semi-circular, thickened within, with 5 teeth, 

 one parietal, two columellar and two palatal; per- 

 istome strongly indented. 



Alt. If, diam. IJ mm. 



V. ventricosa. (Morse.) 



ventricosa, Morse, Ann. N. Y. Lye, VIIL, 1, fig. 1-3, (1865). 



, W. G. Binney, Man. Am. Land Shells, 192, fig. 196, 



(1885). 



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



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



Var. ELATIOR Sterki. 



Larger and more elevated than the type, ovate to oblong, with rather a 

 pointed apex; a strong callus on the parietal wall, into which the plicae merge, 

 a strong tooth-like lamella in the base. 



Vertigo ventricosa elatior, Sterki, L. & F. W. Moll. New Phila., 5, (1894). 

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



Grand Rapids and Beulah, Benzie countv are the only reported localities 

 for the typical form. The variety is more common and has a general range 

 through the lower peninsula. 



Smaller, lighter colored and less ventricose than V. ovata and more regu- 

 larly cylindrical, especially the var. elatior. 



VERTIGO GOULDII (Binney). 



Shell perforate, light chestnut, cylindrically 

 ovate, distinctly striate; whorls rather more than 

 four, ventricose, the last occupying nearly one- 

 half of the axis; aperture lateral; palatal wall de- 

 cidedly flattened or impressed, the impression 

 forming a roundish groove outside and a decidedly 

 projecting angle inside, dividing the peristome 

 into two unequal curves; lamellae five, one pari- 

 etal, two columellar and two palatal, white, 

 Fig. 151. v.gmddii. (Morse.) prominent; peristome thickened, not reflected. 

 Alt. 2, diam. 1, Alt. aper. § mm. 



Pupa gouldii, Binney. Proc. B. S. N. H., I., 105, (1843). 



Vertigo gouldi, W. G. Binney, Man. Am. Land Shells, 190, fig. 191, (1885). 



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



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



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



Generally distributed over the state, but it is apparently not as common 

 a species as ovata, though usually abundant where found. A well marked 

 species, not likely to be confounded with any of the other species found in 

 the state, except, perhaps, V. ventricosa elatior, from which it is to be dis- 

 tinguished by its subcylindrical rather than conical shape, striate surface 

 and ''position of the tooth-hke lamella at the base, somewhat nearer the 

 margin than the end of the columella, the base perceptibly widening at 

 that place." 



