Marlo Krisberg has a nice pictorial (with taxonomic commentary as
referred to by Harry) for Ensis minor/megistus on Lets Talk Seashells.

On 1/6/15, Harry Lee <[log in to unmask]> wrote:
> Bob, you have once again revealed something not quite right with the
> emperor's clothes!
>
> On 11 February, 2014 I looked at the Florida Museum of Natural
> History's holdings of W. Atlantic region Ensis and came away with the
> following impressions:
>     * I have difficulty dealing with the ontogenetic vagaries in
> various morphometrics of the majority of shells from Newfoundland to
> Alabama (AL), e.g., I could not distinguish among the morph in our
> neighborhood (Sunset Beach, North Carolina, Little Talbot Is., FL,
> and St. Augustine Beach, FL) and dozens of other lots from N (S or W
> either) of here. Northern elements grow larger, but there is
> overlap., e.g., five inch shells are not uncommon in NE FL.
>     * The exception: E. megistus is quite different from the vast
> majority of the regional congeners. The small posterior adductor
> scar, its remoteness from the anterior terminus of the pallial sinus,
> and the extremely long, slender anterior adductor scar (> 1/3 the
> length of the valve). I only saw specimens from Tampa Bay to  Alabama
> (AL), and these include a PARATYPE!
> Others have seen a difference between the predominant SE US form,
> often referred to Ensis minor Dall, 1900 [non Chenu, 1843, a European
> species], which runs a little smaller than the New England shell many
> of us collected on Revere Beach during the Boston COA Convention in
> August, 2010..
>
> Lee (2009: 37) pointed out that Van Urk (1971) had shown the
> Plio-Pleistocene Ensis directus (Conrad, 1844) was distinguishable
> from the Holocene E. americanus (A. Gould, 1870), which latter name
> seems appropriate for our Boston (? and NJ) shells.
>
> The second edition of Markus Huber's Compendium of Bivalves, on track
> for publication before this year's COA Convention in Weston, FL,. may
> clarify this miscellany.
>
> As with your earlier inquiry on Angulus agilis et al., (which
> continued in greater detail off-list), more questions than answers
> have been provided.
>
> When you feel the urge to scrutinize another box in your bivalve
> drawer, you needn't open your Pandora's; you've done it already -  twice!
>
> Harry Lee
>
> Van Urk, R.M., 1971. Notes on American fossil Ensis species. Basteria
> 36: 131-142.
>
>
> At 09:59 PM 1/5/2015, Robert R. Fales wrote:
>>Razor Clam Experts:
>>
>>Any suggestions where I might find information on distinguishing
>>between Ensis megistus (Pilsbry & McGinty, 1943 ) and young/small
>>Ensis directus (Conrad, 1843)?  Thanks.
>>
>>Bob Fales
>>Edison, NJ
>
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