PYRAMIDULA SHIMEKII. 



141 



in parallel columns. The wording of the original descrip- 

 tions is preserved, but they are so re-arranged as to bring 

 like characters opposite each to each. 



Zo7iites shimekii Pils. 



A shell of about the size and 

 shape of Z. nitidus. 



Surface sculptured with strong - , 

 curved riblets above, rather 

 finely striated beneath. The 

 outer three (whorls) ribbed- 

 striate. 



Spire low-conical. 



First (or nuclear) whorl planor- 

 boid but noticeably projecting - , 

 a trifle matnmillated, snowy- 

 white, smooth and polished. 



Whorls Ay 2 . 



Aperture oblique, nearly circu- 

 lar, the ends of the peristome 

 approaching. 



Alt. 4, greater diam. 5%, lesser 

 5% mm. 



Width of umbilicus 1% mm. 



Pyramidula cockerellii Pils. 



Shell having the general shape 

 of P. striatella*. 



Very irregularly wrinkle-striate, 

 some specimens unequally 

 ribbed in places above and at 

 the margin of the umbilicus. 



Spire convex. 



The first whorl a little protrud- 

 ing, whitish-corneous and 

 glabrous when unworn. 



Whorls 4^. 



Aperture oblique, rounded, the 

 penultimate whorl cutting out 

 a segment of about one-fourth 

 the whole circle of the thin 

 and simple peristome. 



Alt. 2.8, diam. 5.5 mm. (from New 



Mexico) 

 Alt. 3.2, diam. 6.5 mm. (from 



Colorado). 



Width of umbilicus "contained 

 about 3.7 times in that of the 

 shell." — hence about l^mm. 



The surface-markings are variable in both forms. Some- 

 times the upper surface is quite regularly ribbed, and again 

 merely "irregularly wrinkle-striate," while the lower sur- 

 face may or may not show plications or coarser striae 

 around the margin of the umbilicus. The large series of 

 fossils in the author's collection especially shows much 

 variation in these characters. 



The dimensions in the original descriptions would indi- 



* All of the shells in the author's collection resemble Z. nitidus much 

 more closely. 



