According to Kozloff in "Invertebrates of the Pacific Northwest" they are
different.  The pycna is supposed to have zigzags and the baetica not.  The pycna is
not supposed to be found north of Oregon whereas the baetica has a bigger range.
Also the pycna has different height to width ratios, but since my book is not here I
can't exactly remember what the difference is.
I may have started this question or else it's a coincidence, but I found some
Olivellas on Vancouver Island that match the pycna more closely than the baetica
according to both Kozloff and Abbott's American Seashells.  Maybe some workers
consider then synonymous, but I have not found any mention of that so far.
So, are Kozloff's and Abbott's descriptions incomplete, or can pycna be found north
of Oregon or are they really synonymous????

Dan Yoshimoto wrote:

> Dear Comrades in Shells,
>         I just received a note from a Canadian friend requesting info on
> Olivella pycna.  He has collected a small Olivella from Vancouver Is.,
> Canada and has not seen it described in any Canadian literature.  He's
> checked Abbott's 2nd edition of American Seashells and gets the same
> description as he gets from other literature on O. baetica.  Can someone
> offer a difference between the two species or are they synonymous?
> Dan Yoshimoto
>
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