Monday, January 3, 2011

A Big Mystery

Through some good fortune the large storm that dumped snow over much of the east coast stayed to our east and left us with relatively snow free ground. So during the holiday break I went to Nescopeck State Park to do a little combo snailing/birding. Birding was absolutely dead. I had hoped for winter finches like Redpolls and Siskin, but arrived to find the feeders empty, as was much of the park. With bird life at nil, I turned my attention fully to snails.

Overall I was very pleased with my snailing. I found my very first Vitrina angelicae (Eastern Glass-Snail) shell sitting in a pile of leaves on top of a flat rock. I also found some Triodopsis tridentata and a couple Stenotrema  hirsutum. Another interesting find was a 6 whorled heliciform shell that doesn't match up with anything in my database (the one I built for my iphone app), so I'll have to look into more.

Most importantly I was pretty excited to find what is my largest land snail yet. The above picture is of that snail. The shell was in/under a log that looked like it  had a hole for some rodent. My best guess is that this fellow became dinner. But luckily, there seems to be enough information left in the shell to make an identification.

First, obviously, we can say it's heliciform (72 matches). The width measure 28.4mm (11 matches) and it is imperforate (6 matches) with a reflected lip(5 matches). No teeth are present(this has 3 options- no teeth, teeth and teeth sometimes present- it always pulls the sometimes matches plus the yes or no depending on input). Plugging that into my app, I came up with 3 suspects: Mesodon zaletus, Neohelix albolabris, and Webbhelix multilineata.

From there it's time to take to Pilsbry but not before first taking a look in the microscope for any microsculpture I could glean (unfortuneately I haven't 100% finished to database for things like striae, puncta, etc.) . But there is what seems to be some crucial evidence-- indented radial striae.

Regarding microsculpture and the aforementioned snails according to Pilsbry:

Mesodon zaletus:
Later whorls with sculpture of fine oblique striae and microscopic spiral lines, which are typically rather weak or subobsolete, but sometimes distinct.
Neohelix albolabris:
Later whorls with sculpture of fine oblique striae and minute, crowded, incised spiral lines.
Webbhelix multilineata:
... the rest with fine sculpture of oblique striae, rather weak spiral engraved lines in their intervals.

Here is the microsculpture.

There seems to be no mention of the spiral lines being indented with Mesodon zaletus. Webbhelix multilineata usually has color bands (although Pilsbry mentions a mutation known as Webbhelix multilineata mut. alba that is bandless and can occur with the banded shell populations). However, I believe the description of 'crowded, incised spiral lines' sees to hit the mark.

So, I believe this mystery solved. It is the snail Neohelix albolabris (common name, Whitelip).

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