130 Zoology of Colorado 



are regularly sinistral, as it is called. The reversed spiral begins 

 with the first cleavage of the egg, and after that cannot be altered. 

 In the Hawaiian Islands there are land snails which may be in- 

 differently sinistral or dextral. Thus, of six examples of Auri- 

 culella auricula before me, four twist to the right, two to the left. 

 Another Colorado Oreohelix, described by Pilsbry as recently as 

 1912, is 0. hendersoni. It was first found along Little Thompson 

 Creek, about ten miles northwest of Longmont. The shell is 

 smooth, depressed or somewhat elevated, without distinct color 

 bands, though these are more or less visible on the first whorls. 



When we go south of the Colorado border, into New Mexico, 

 we find species of a very different genus of snails; the shells brown, 

 bandless, usually shining, the aperture with a heavy white lip. 

 They mostly have a diameter of about 15 mm. When these 

 snails were first discovered, they were placed without question 

 in Polygyra, which includes many common species of the eastern 

 states. But the Rev. E. H. Ashmun, an indefatigable collector 

 of snails, obtained living specimens, and dissection showed at 

 once that we had a perfectly distinct genus, not even closely re- 

 lated to Polygyra. It was accordingly named Ashmunella, and 

 since then very numerous species have been discovered. Al- 

 though this genus must have inhabited New Mexico and Arizona 

 for countless years, no traces of it have been found in Colorado. 

 It must be said, however, that our southern border has never 

 been properly searched, and some one may yet be rewarded by 

 the discovery of a Colorado Ashmunella. 



The form of Oreohelix cooperi found in the loess of Iowa was 

 somewhat distinctive, and was named iowensis by Pilsbry. In 

 the same manner, a small depressed coiled snail common in Colo- 

 rado has a representative in the Iowa loess; but as it happened, 

 the fossil was the first to receive a valid name. Therefore Gony- 

 odiscus shimek.ii is the name of the Iowa fossil, and G. shimekii 

 cockerelli is the subspecies still living in the Rocky Mountains. 

 Both names are due to Pilsbry. 



Very elegant little snails, less than three and a half mm. 

 diameter, belong to the genus Vallonia. There is a distinct lip 

 to the aperture, and the surface of the shell may be smooth (the 

 introduced V . pulchella) or with fine transverse ribs. Over thirty 

 years ago, it was customary to refer these shells to well-known 



