Posted: May 18 2012

 Ensis megistus Pilsbry & McGinty, 1943, Minor Jacknife Clam

[(or, Ensis leei Huber, 2015 (see below)]

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Posted: Mar 5 2016, Harry Lee:

"The shells in this fine report are not Ensis megistus Pilsbry and McGinty, 1943.

On 11 February, 2014 I looked at the Florida Museum of Natural History's (FLMNH's) extensive holdings of W. Atlantic Ensis and came away with the following impressions:

• Accounting for the ontogenetic vagaries in various morphometrics of shells from Newfoundland to Alabama (AL), I could not distinguish among the morph in our neighborhood (Sunset Beach, NC, Little Talbot Is., FL, and St. Augustine Beach, FL) and dozens of other lots from N (S or W either) of here. Northern elements, identified as E. directus Conrad, 1844 by many authors over the years, grow larger, but there is considerable overlap in all characters, e.g., five inch shells are not uncommon in NE FL.

• E. megistus is quite different from the the preceding, which is the only regional congener and comprises the overwhelming majority of the FLMNH W. Atl. lots. 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) are distinctive. I only saw a few specimens from Tampa Bay to Alabama (AL), and these include a PARATYPE!

At that time I concluded that the predominant SE US form, often referred to Ensis minor Dall, 1900 [non Chenu, 1843, a European species] by authors, and the often larger New England shell, E. directus of authors, collected by many (including Huber and I) on Revere Beach, MA during the Boston COA Convention in August, 2010, constituted a conspecific cline. For this species I thought the Solen ensis americanus Gould in Binney, 1870 was the first available name (see Lee (2009).

Agreeing with Lee (loc. cit.), Huber (2015: 559-560) considered Ensis directus Conrad, 1844 to be limited to the Pliocene but added that the Gould taxon was unavailable due to junior homonymy with Solen americanus Chenu, 1843, itself a junior synonym of Siliqua patula, another, yet distinctive, denizen of Revere Beach. Unable to find another available name, Huber proposed Ensis leei for this species, which also counts among its misidentifications/synonyms, E. megistus of authors, not Pilsbry and McGinty, 1943.

Short version: The subject odf this vignette is Ensis leei Huber, 2015.

Huber, M., 2015. Compendium of Bivalves 2. A Full-Color Guide to the Remaining Seven Families. A Systematic Listing of 8'500 Bivalve Species and 10'500 Synonyms. ConchBooks, Hackenheim, Germany. 907 pp., incl. numerous color figs + CD-ROM. May.

Lee, H.G., 2009. Marine Shells of Northeast Florida. Jacksonville Shell Club, Inc. 204 pp. + 19 color plates. 28 May."