142 NATURAL HISTORY BULLETIN. 



cate that the fossil is much more elevated. The fossils 

 however exhibit so much variation in this respect that 

 the flattest recent shell in the author's sets easily falls 

 within its range. The dimensions of two fossil specimens 

 from the collections made at Iowa City illustrate this: 



Flat form : 



Great, diam. 7.4 mm.; alt. 3.5 mm., umbilicus 3 mm. 



Elevated form: 



Great, diam. 6.5 mm.; alt. 4.2 mm.; umbilicus 1.7 mm. 



This may be compared with the dimensions given in the 

 original description, and with those of the two largest 

 shells in two of the author's recent sets. 



La Belle, N. Mex. : 



Gr. diam. 6.2 mm.; alt. 3 mm.; umbilicus 1.9 mm. 



Red River, N. Mex.: 



Gr. diam. 7.0mm., alt. 3.7 mm.; umbilicus 1.9 mm. 



The original description of P. cockcrcllii also contain the 

 following additional description which applies equally well 

 to the fossils: 



"The rest (of whorls other than apical) convex, 

 regularly widening, separated by a deep suture ; last whorl 

 obtusely angular at the periphery in front, becoming 

 rounded on its later portion; base well rounded, the 

 umbilicus showing all the whorls. . . The greatest diameter 

 of aperture contained about 2.4 times in that of shell." 



The comparison of both the descriptions and the shells 

 of Z. shimekii and P. cockcrcllii therefore establishes their 

 identity. As Zonitcs shimekii was described in 1890, and 

 Pyramidula cockcrcllii in 1898, the former specific name 

 will stand, but the species must be transferred to the genus 

 Pyramidula {-Palula) , and the name becomes Pyramid- 

 ula shimekii (Pils.) Shimek, of which P. cockcrcllii Pils. 

 is a synonym. 



