1890.] NATrntAL SCirCNCKS OF PIIILAnKF.rillA. 297 



hroiider above the iniddle, liaviiig more immerou.s whorls, the hi.st 

 one more ascending on the penultimate ; the ridge back of the 

 outer lip is much stronger than in muscorum, and the lip itself less 

 broadly expanded. The same characters will separate the species 

 from P. umsconim var. Blandi. 



Zonites Shimekii, Pil.'^bry. (PI. V. figs. !( 10, 11 ). 



A shell of about the size and shape of Z. nitidus ; moderately uni- 

 bilicated ; chalky-white, without epidermis, on account of its fossil 

 condition. Surface scul{)tured with strong curved riblets above, 

 rather finely striated beneath. S2)ire low-conoidal ; apex obtu.se ; 

 first (or nuclear) whorl i)lanorboid but noticeably projecting, a 

 trifle nuimmillated, snowy-white, smooth and polished. Whorls 4-2, 

 the outer three ribbed-striate. Aperture oblique, nearly circular, 

 the ends of the peristome approaching. 



Alt. 4, greater diam. 5 ', lesser 51 mm. ; width of umbilicus 1 1 mm. 



Habitat, Loess formation (Quaternary) of Iowa, at Iowa City, la. 



This species has been familiar to me for some years, under the name 

 oi Zonites limatulus. It agrees with that form in the number of 

 whorls and sculpture, except that the Shimekii is more sti'ongly, reg- 

 ularly ribbed above. It differs from limatulus in being far more 

 r()l)ust, more elevated, with rounder mouth and narrower, deeper 

 umbilicus. Upon comparing specimens of the two species, I am sur- 

 prised that they were ever confused ; for, except in sculpture, the 

 Z. Shimekii is far more like Z. nitidus than to Z. limntulus. The 

 .specimens described and figured were collected by Prof. B. Shimek, 

 now of Lincoln, Nebraska. 



This form is interesting as being the only well-defined species of 

 Loe.ss fossil which seems to have become extinct ; although there are 

 a number of others, such as Heliciaa occulta and Patula strigosa var., 

 which survive in greatly reduced numbers in a few limited locali- 

 ties, or only in a distant ])art of the country. 

 Vaginulus Schivelyae, Pilsbry. PI. V, figs. 0, 7, S. 



Description of alcoholic specimens : 



Light yellowish-gray above with two ill-defined longitudinal dark 

 bands formed by the aggregation of l)lack flecks and dots on either 

 side of a dorsal light line. There are dark flecks scattered s])arsely 

 over the rest of the surface ; and the middle area of the back is 

 more or less smoke-colored ; the lateral margins are grayish. 



