Microphysula cookei

Microphysula cookei (Pilsbry, 1922)
Vancouver Snail

  • Zonitoides cookei Pilsbry & Cooke 1922: 38, nomen nudum.
  • Zonitoides cookei Pilsbry 1922: 38, fig. 1.
Microphysula cookei
Microphysula cookei; Astlais Mountain, Babine Range, Skeena Mountains, BC (RGF 97.196.2019); width 4.1 mm).

Identification. Shell subdiscoid. Spire only slightly raised. Whorls ca 5, rather closely coiled and slowly enlarging. Suture moderately indented. Periphery of last whorl rounded. Aperture narrowly lunate, edentulous. Lip thin, simple. Umbilicus small, ca ¼ of shell width. Protoconch smooth. Teleoconch smoothish, with weak incremental lines and fine, close, spiral lines. Shell with a silken lustre, translucent, milky whitish. Width to 4.4 mm (wider than high).

Animal pale, whitish; body, through shell at spire pale pinkish.

The two species of Microphysula are difficult to distinguish. Pilsbry (1940) suggested that M. cookei is slightly smaller and with less tightly coiled whorls than M. ingersollii. In practice, these species seem inseparable on conchological grounds. Identifications of Canadian material are more apt to be made based on geography: coastal populations have been called M. cookei while those from the Rocky Mountains, M. ingersollii. Further study of this problem is necessary.

Habitat. Mainly wet, montane coniferous forests and vegetated rockslides at and below tree line (Forsyth 2001); low-elevation riparian mature mixed-wood forest on Vancouver Island. The “pine forest” at Cameron Lake, Vancouver Island, mentioned in the original description by Pilsbry (1922) is possibly erroneous, as the tree species possibly were more likely to have been Douglas-fir (Pseudotsuga menziesii).

Canadian range. BC: Vancouver Island; coastal ranges on the mainland (Boundary, Coast, Skeena, Bulkley, and Cascade ranges).

Etymology. Named after Dr Charles Montague Cooke Jr (1874–1948), of Honolulu, Hawaii, who was a friend and malacological collaborator of Henry A. Pilsbry. In July and August 1918, Cooke collected land snails at a couple of places on Vancouver Island, including this species at Cameron Lake.