32 A Canadian Arctic Expedition, 1913-18 
NOTES 
Trichotropis borealis Sowerby 
This species has generally been confounded with its European analogue, 
but a careful inspection is sufficient to show the distinctness. Sowerby’s 
species was described from America. 
Pseudamusium andersoni Dall 
The collector notes that this species was cast up on the beach in windrows 
two or three feet high, like dead leaves, only far thinner and more fragile. The 
shells are usually worn so that the more delicate surface is lost and it becomes 
difficult to distinguish it from P. grénlandicus. This species was described in 
1919 from specimens dredged in about 50 fathoms in Dolphin and Union strait. 
Pseudamusium ringnesia n. sp. 
Shell small, translucent white, extremely thin, nearly flat; disk nearly 
circular, sculptured with about 30 thin, sharp, régularly concentric lamellae 
with much wider interspaces; the outer edge of these lamellae is produced and 
bent down but not attached at the distal edge, covering about two-thirds of the 
interspace in front of the lamella; these loose margins are somewhat wavy and 
narrower posteriorly and stop short on a line radiating from the umbo toward 
the posterior basc; at the point of termination they expand into postules form- 
ing a line bordcring a posterior area, sculptured only by close, low, concentric 
lamellation; the true surface of the valve is not undulated but sculptured with 
fine radial striae; the whole of this lamellation is of extreme fragility and liable 
to be affected by a touch; the hinge margin is straight, the anterior ear larger 
than the posterior, with a close, minute, subspinose, concentric lamellation: the 
posterior ear with only lines of growth; the hinge is minute, the interior of the 
disk smooth, the external sculpture showing through. Height 12 mm.; breadth 
13 mm. 
Only one left valve was obtained but the sculpture is quite unique and the 
shell is not undulated, the appearance of undulation arising from the folded- 
over edges of the lamellae. 
Type.—Victoria Memorial Museum, Ottawa (Mollusks, No. 4376). Figured 
on Plate 4. 
Yoldiella obesa Stimpson 
This has been identified with Y. lucida Lovén, but the uncertainty leads 
me to utilize the name which certainly applies. 
Lora scalarioides G. O. Sars. 
There is only one slightly eroded specimen which is referred to Sars’s 
species. It does not quite agree with specimens so named in the Jeffreys collec- 
tion but I hesitate to separate it in the absence of a larger series. 
Euspira affinis Gmelin 
This is the shell referred to Gmelin’s species by Jeffreys. It is nearest to 
E. pallida Broderip and Sowerby, of the western arctic but has a less elevated 
spire and a different umbilical callus. Whether it is really the shell Gmelin had 
in mind is impossible to be certain, but it seems to have been generally accepted 
as such by European authors. 
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