10 
Gonyodiscus shimekii (Pilsbry 1890) 
Plate I, figure 8 
1890. Zonites shimekii Pilsbry, — Nautilus, vol. 4, p. 3. 
1890. Zonites shimekii Pilsbry, — Proc. Acad. Nat. Sci. Phila., 1890, p. 
297, pi. 5, f. 9-11. 
1891. Zonites shimekii Pilsbry,- — Nautilus, vol. 5, p. 39, pi. 2, f. 9-11. 
1898. Zonitoides shimekii Pilsbry, — Nautilus, vol. 11, p. 131 (merely 
catalogued) . 
1901. Pyramidula shimekii Shimek, — Bull. Lab. Nat. Hist. State Univ. 
Iowa, vol. 5, p. 139. 
Material Examined 
No. of 
Geol. Surv. 
spec. 
Locality 
Collector 
Date 
Cat. No. 
225 
Kananaskis, Alberta 
J. Macoun 
1885 
2937 
It is a considerable surprise to find this species, heretofore known in 
the living state only by the subspecies cockerelli Pilsbry — which is an in- 
habitant of the southern Rockies — flourishing so far north and in such num- 
bers, especially since neither it nor cockerelli has yet been encountered in 
Montana, whereas typical shimekii was originally described as a fosssil 
from the Iowa Loess. The writer has had no opportunity of examining 
any Iowa shimekii , but upon comparison with cockerelli from Elorado, 
Colorado, sent him by Junius Henderson, the Albertan shells prove to 
run a little larger, are lighter and greyer in colour, are more robust, and 
seem thicker shelled, and the axial ribs on the upper surface of the whorls are 
more even, more sharply cut, and probably more numerous. Examples 
of cockerelli from Colfax county, New Mexico, collected by Ashmun, are 
rather different in appearance from either the Coloradan or Albertan shells. 
The possibility was considered that the Canadian specimens represent a 
new subspecies, but, firstly, there seemed too little comparative material 
available to render such an opinion safe, and secondly, it was thought 
possible that a similar relation might exist between the Albertan race and 
the typical Loess form to that suggested by Pilsbry (1916, p. 357) for Oreo- 
helix cooperi stantoni (Dali) of southwestern Saskatchewan and the Loess 
O. c. iowensis (Pilsbry). Thereupon a few of the present specimens were 
sent to Dr. Pilsbry, with the request that he compare them directly with 
the types of both shimekii and cockerelli. He replied (November 24, 1920) 
as follows: “The P, shimekii from Canada are about intermediate be- 
tween typical shimekii and cockerelli. The last should have a noticeably 
wider umbilicus. In your shells the umbilicus is equal to that of the most 
openly umbilicate of the original shimekii. The distinction of the race 
cockerelli is probably of doubtful expediency, though usually it is more 
depressed and more open beneath.” It, therefore, seems reasonable to 
refer the Albertan race outright to shimekii, whether or not one follows 
Shimek (op. cit., pp. 140-143) in reducing cockerelli to the synonymy. 
