Hiatelloidea & Basterotiidae | ID Keys | Marine Bivalve Shells of the British Isles

#1

Beaks close to the midline

Beaks towards the anterior

#2

Outline elongate oval, hinge teeth rudimentary, periostracum persistent dark brown to black [Arctic]

Outline subquadrate with a median sulcus, gaping widely, single cardinal in LV

#3

Shell initially biangulate posteriorly with 2 radial ridges but becoming eroded, LV with 2 small cardinal teeth

Shell not biangulate, hinge with a single cardinal peg or lacking teeth

#4

Boring into calcareous rocks, posterior radial angles lacking spines

Nestling in crevices, posterior radial angles persistent often bearing short hollow spines

#5

RV with a single flange-like cardinal, posterior angle rounded

Hinge lacking teeth, posterior angle subacute