| Term | Definition |
| QUADRATE |
Square or rectangular in general outline; applied to the outline of shells which is formed by nearly straight lines meeting at approximately right angles; see also: HEXAGONAL; POLYGONAL; OCTOGONAL; RHOMBOID; SUBQUADRATE; TRAPEZIFORM; TRAPEZOIDAL. See other bivalve shapes. Photo: Mysella sp. undet. |
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| SUBQUADRATE |
Not quite QUADRATE, but nearly so; see also:
SUBELLIPTICAL. See other bivalve shapes. |
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