GASTROCOPTA, NORTH AMERICA, WEST INDIES. 69 



Pupa hordeacea Gabb, BINNEY, Terrestrial Mollusks, v, 

 1878, p. 205, f. 109 (bad). STERKI, Nautilus, iv, 1891, p. 141; 

 vi, 1892, pp. 4, IQl.Bifidaria hordeacea Gabb, PILSBRY, Nau- 

 tilus, xi, p. 117. Not Pupa hordacea Gabb. Bifidaria procera 

 cristata PILSBRY and VANATTA, Proc. A. N. S. Phila., 1900, 

 p. 593, pi. 22, f. 4, 5. WALKER, Occ. Pap. Mus. Zool. Univ. 

 of Mich., no. 15, 1915, pp. 4-11 (distribution). 



While related to G. procera by its shape, color and size, this 

 species differs by the simpler angulo-parietal lamella, which is 

 not bifid at the summit, in a front view, and by the stronger 

 crest behind the lip, which is further back than that of pro- 

 cera. Having collected some thousands of the species in many 

 places, and carefully examined a great number, I find none 

 in any way transitional to procera. 



The variation in size is as great in most lots as in the re- 

 lated species. The largest and the smallest noticed in a lot 

 from Tempe measure, length 3.2, diam. 1.3 mm., and length 

 2.3, diam. 1.1 mm. (pi. 13, fig. 6). The callous below the 

 columellar lamella varies from rather low to a distinct tooth, 

 but it is rarely so well developed as in most specimens of B. p. 

 mcclungi. The projection on the columellar side of the pari- 

 etal lamella also varies slightly, but it is never so strong as in 

 well-developed duplicata. 



G. cristata may be found in the debris of the Rio Grande 

 almost anywhere, being brought in by tributary washes from 

 the hills. Whether it actually inhabits the country as far 

 down as Laredo and Hidalgo seems doubtful. It occurs also 

 in the Mississippi River drainage in Oklahoma, and in the 

 Colorado River drainage as far west as Yavapai Co., Arizona. 



20. GASTROCOPTA RIOGRANDENSIS Sterki, n. sp. PL 12, figs. 



9,10. 



The shell is shortly rimate; slowly tapering, less cylindric 

 than G. procera, cinnamon or sayal-brown, paler towards the 

 summit, weakly, irregularly striate, composed of 5% strongly 

 convex whorls, the last one impressed over the lower palatal 

 plica, and having a narrow, rather strong crest parallel to 

 the lip a short distance behind it (fig. 9). The aperture has 



