Hi Ellen,

I'm a New England collector also, presently in Rhode Island, formerly in
Massachusetts. But I still do more collecting in MA than in RI.  The two
species you mention can be confusing at first, and as you say the book
illustrations are not very helpful, but once you get used to them you can
tell them apart at a glance. L. saxatilis has a taller spire, more impressed
suture, less well defined spiral sculpture, and a less inflated body whorl.
Interestingly, L. littorea has a noticeably sharper apex, even though it is
a much larger shell, because of the smaller size of its embryonic shell.
But these facts are not particuilarly useful for quick field identification.
Color is often helpful.  Small L. littorea are almost always black, whereas
L. saxatilis come in many shades - brown, yellow, white, gray, and often
with lighter color bands, which L. littorea never has. Black L. saxatilis
are possible, though not common.  Perhaps the easiest criterion to use is
interior color.  L. littorea has a distinct black band along the inner edge
of the lip, but is lighter colored deeper inside.  L. saxatilis is often
chocolate brown interiorly, or may be the same color as the exterior of the
shell, but in any case does not have the dark band along the inner lip.

I have collected L. saxatilis at Manomet Point in Manomet, MA.  This
location is also where I have found the largest L. littorea I have seen
anywhere - some over 40 mm.  There are many huge intertidal boulders here,
covered with Fucus (rockweed).  At low tide you can walk out a bit to where
some of the larger boulders are.  Grab a handful of Fucus and shake it over
a box or other container and most likely at least a couple of dozen L.
obtusata will fall into the box.  Do this a half dozen times and you will
probably have over a hundred L. obtusata.  Look through them carefully and
you will most likely find several L. saxatilis mixed in. Out in the
mid-tidal area anything that is not L. obtusata is most likely L. saxatilis.
The L. littorea are not primarily rockweed snails.  They stay in closer to
shore where there is less rockweed, and they can crawl on bare rocks.

If you do collect here, be careful.  The vertical tidal range is about 8
feet, and the tide comes in pretty fast. If you are a good distance out and
are not alert, you may find yourself cut off from the shore by a fast-moving
channel of water.

Regards,
Paul M.

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