Studies on the anatomy and ecological distribution of Dentalium texasianum Philippi 1848 in West Bay of the Galveston Bay complex (Mollusca: Scaphopoda).

Dredged sediment samples collected from 54 stations in West Bay of the Galveston Bay Complex produced 370 shells of the scaphopod Dentalium texasianum Philippi 1848. Associated physiographic, hydrographic and sediment data suggest D. Texasianum is a subtidal species which inhabits porous substrate and is tolerant of varying temperatures and salinities. The abundance and distribution of empty shells indicate D. texasianum was recently alive in West Bay but was not during the sampling period. It was suggested that living specimens were absent because of environmental conditions beyond the range of tolerance for D. texasianum, because of pollution from nearby housing developments or because it is a species which infrequently settles in West Bay and dies before reaching its reproductive stage. Studies on variation in shell form and sculpturing revealed that the subspecies D. texasianum cestum named by Henderson (1920) is unnecessary as it fits within the range of variation for D. texasianum texasianum found in this study. Observations made on the anatomy of preserved specimens collected from West Bay in 1966 and 1967 showed several differences between D. texasianum and the eurasian species described in the literature. Descriptions are given for a central lumen in the foot and a pair of semilunar valves near the posterior end of D. texasianum which had not previously been described.