Two new tretodictyids (Hexactinellida : Hexactinosida : Tretodictyidae) from the coasts of North America

Abstract

Two new species of the hexactinellid family Tretodictyidae, both collected by submersible, have been discovered off the coasts of North America. The Pacific species, Tretodictyum montereyensis n. sp., has an unusual skeleton with a fused cortex added over the usual tretodictyid system of ridges and grooves on the dermal surface. The Atlantic species, Hexactinella carolinensis n. sp., is unusual among its congeners in having swollen nodes on the dermal skeleton. Diagnoses of both genera have been modified to accommodate the new findings. The fine diactins of both species are found to have shallow brackets and short barbs, confirming their uncinate nature. Addition of these two species raises the number of known North American tretodictyids from one to three.