82 AMERICAN SPECIES OF VERTIGO. 



BLATCHLEY and DANIELS, 27th Ann. Eep. Dep. Geol. and Nat. 

 Res. Indiana, 1902, p. 587, 632 (Kosciusko, Marshall and 

 Steubeu comities, Ind. WALKER, Moll, of Michigan, 1906, 

 p. 516, f. 149 (Dewey's Mill, near Grand Rapids, type loc. ; 

 Eaton, Bay and Washtenaw counties, Mich.). 



"In one example the inferior parietal tooth is wanting, in 

 another the basal only trace-like, and in a third the same is 

 double, as frequently found in V. ovata. With the latter 

 species, V. morsel has much resemblance, especially iii the 

 aperture: the configuration and the 'teeth' are the same, but 

 the inferior columellar, and the two principal parietals, are 

 rather larger, and markedly directed upward. The main dif- 

 ference is in the number and relative size of the whorls : while 

 in V. ovata they are five, and rapidly increasing, the last pre- 

 dominating, in our species there are six, slowly increasing, 

 the last, and consequently the aperture, comparatively small. 

 This is a radical difference, and gives the shell quite another 

 aspect, so that there can be no question about its being dis- 

 tinct. But T 7 . morsei is also decidedly larger, V. ovata not, 

 or little, exceeding 2 mm. in altitude" (titerki). 



The species is named in honor of Prof. E. S. Morse. 



Specimens determined by Dr. Sterki measure : 



Length 3, diam. 1.5 mm.., 6^ whorls. 



Length 2.6, diam. 1.3 mm., 6 whorls. 



The color is from auburn to chestnut-brown. There is a 

 distinct crease behind the lip, from the crest to the lip- 

 point, and over both palatal plicae there is a wide depression 

 externally. Dr. Sterki writes that out of 100 specimens ex- 

 amined from the marl of Erie Co., Ohio, 10 have an infra- 

 parietal, quite small or vestigial. 



While it stands very close to V. ovata,, this species does not 

 appear to iiitergrade, so far as seen. It is the largest Vertigo 

 known. 



4. VERTIGO OVATA Say. PL 6, figs. 1 to 4, 7. 



' ' Shell dextral, subovate, brown ; apex obtuse ; whorls five, 

 glabrous ; suture not very deeply impressed, body whorl in- 

 dented near and upon the labrum ; aperture semioval ; labrum 



