Hi Marcus,

Not sure what you mean by “exactly as the description shows.”  There is no
description in the link, only pictures.  Do you mean one of the four on the
black and white plate?  I’m guessing figures 1-4 are M. modulus (can’t read
the label too well).   I do not have Abbott’s monograph from Johnsonia.

I have no material for M. carchedonius.  M. modulus around Florida is quite
variable and also quite variable from juvenile to adult (assuming indeed
they are all the same species).  I go along with the approach that if at
least some (or most adults) in a locale have a brownish purple columella
tooth, then the population is M. modulus.  Since M. carchedonius is reported
to always have a white columella tooth, but M. modulus often does too, I
find it hard to accept that when mixed shells (with brownish-purple and all
white columella teeth) are found in the same location, that two species are
involved.  I don’t think it’s rational to expect this.  Hoping for the day
when someone takes a good look at this issue.

Marlo
merritt island, fl

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Marcus Coltro wrote:

I found an old Conch-L post from Marlo about Modulus modulus x carchedonius,
reproduced on "Let's Talk Seashells."  Then checked several lots from Bunnie
Cook's collection and my own database - she identified specimens from St.
Croix as M. carchedonius (a good thing about her shells is that all info is
100% reliable!).  From Johnsonia's pictures and description I am not sure if
I agree with her identification - plus, the specimen pictured as
carchedonius looks more like catenulatus (West America) than anything else!

I wonder if anyone has ever found any specimen exactly as the description
shows. Modulus modulus is very variable and young specimens tend to have
angulated shoulders and may have columellar tooth white.

Any thoughts?

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