Identificaciones de gwenlh

The Robust Lancetooth Snail was First reported from Montana in 1956. With it's large but short shell, reaching sizes of 21-31mm in diameter and 8-12 mm in height, it is quite successful in hiding between rocks and under the bark of fallen trees. The shell commonly comes in colours ranging from dull yellow to olive green in colour. Whereas the head, neck, and body of the snail is creamy white in colour. The Robust Lancetooth Snail is an omnivorous species and will eat anything from earthworms to beetle larvae, and even its own kin.

Sources 

- http://10000thingsofthepnw.com/2020/11/28/haplotrema-vancouverense-robust-lancetooth-snail/

- https://islandnature.ca/2009/10/searching-for-the-robust-lancetooth/#:~:text=The%20robust%20lancetooth%20is%20a,(including%20their%20own%20species).

Menegazzia because of the perforations, and taking the chance that this is M. subsimilis based on the choice of two possibilities on the Ways of Enlichenment website

growing on living Alnus rubra trunk