The following from Wagner, Review of the European Pectinidae, Vita Marina
Vol.41, No. 1 pp.3-48 ?year may be of help in the F. proteus / F. glaber
question

(F. proteus) This species is ofter (partially) confused with F. glaber by
various authors...It can be distinguished rather easily by the angular
outline of the disk (rounded outline in F. glaber), comparatively less
deeper shell in respect to height and width, the lower number of primary
ribs, and the pairwise set of internal ribs.  From F. flexuosus it can be
distinguished by the angular outline of the disk also (rounded in F.
flexuosus); comparatively less deeper shell in respect to its height and
width; its larger size; being subtranslucent (not translucent in F.
flexuosus); smaller anterior auricle in respect to the posterior ones; and
top angle. [top angle in F. flexuosus 88-95 degrees; in F. proteus 98-102
degrees]
  Hope this helps.

Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History, Pittsburgh, PA
Assistant Professor - Family Medicine

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