AMERICAN SPECIES OP VERTIGO. 127 



ures, length 1.9, diam. 1.2 mm., and is closely striate on the 

 penult whorl. 



Specimens from the loess of Iowa are quite variable in 

 form and size. Those figured measure : 



Length 2.65, diam. 1.45 mm. (page 124, fig. 2a, Iowa City). 



Length 2.4, diam. 1.35 mm. (page 124, fig. 2, Iowa City). 



Length 2.3, diam. 1.2 mm. (plate 10, fig. 2, Des Moines). 



The smallest of these, pi. 10, fig. 2, is rather strongly striate, 

 much as in V. concinnula. 



It has also been found by Mr. A. A. Hinkley in loess at 

 New Harmony, Indiana, according to Dr. Sterki. 



In a series from Dyea valley, Alaska, the size varies from 

 2.4 x 1.4 to 2.65 x 1.4 mm. The crest is rather strong. The 

 teeth vary from typical to slightly larger, and in some of 

 them a small angular lamella is added. The lot is inter- 

 mediate between modesta and mut. parietalis, or rather, it in- 

 cludes both forms. A specimen was figured in Proc. A. N. S. 

 Phila. 1900, pi. 23, fig. 2. 



Specimens taken on Norton Bay, Alaska (R. C. McGregor) 

 are deficient in teeth, an upper palatal fold being absent 

 (page 124, fig. 3), the parietal and columellar lamellae small. 

 Length 2.4 to 2.6, diam. 1.4 mm. It agrees rather closely 

 with the description and figures of V. arctica Wallenb., de- 

 scribed from Lapland, and I have no doubt is identical with 

 the form listed as arctica from Port Clarence by Westerlund 

 (Vega-Exped. Vet. Arbeten, iv, 163) ; yet I can but regard it 

 as a form of modesta, in view of the fact that it is in the 

 V. modesta area, and that a similar deficiency in teeth occurs 

 in forms of modesta found in the loess of Iowa and in Cali- 

 fornia. I do not here consider the question whether V. 

 arctica is distinct from modesta for the reason that I have no 

 Lapland examples of arctica. 



Pupa borealis Morelet is generally admitted to be identical 

 with decora (modesta). A translation of the description 

 follows: Shell rimate, ovate-oblong, glossy, diaphanous, ful- 

 vous-corneous, regularly striate under the lens; whorls 6, a 

 little convex, the last compressed at base, forming a moder- 

 ate excavation. Aperture somewhat rounded oval, moderate, 



