The morphological groups Elphidium incertum (Williamson), E. incertum of Cushman, E. clavatum Cushman, E. subarcticum Cushman were compared by observing external morphology of representative populations from Long Island Sound. Results suggest that all but the second are distinct enough to be recognized as species. To test the hypothesis, the groups were discriminated on external morphology and eight characters by which groups are distinguished were measured and/or scored on 30 individuals from each. These variates were then compared along canonical axes. Further comparison was possible through consideration of presence or absence of organic inner lining and radial wall, and granular wall structure. All evidence indicates that these species are represented.

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