Plastic clay at the mouths of the Mississippi River contain 39 species in 32 genera of cheilostomes and 4 species in 4 genera of cyclostomes. Cheilostomes are similar to those now living in the Gulf of Mexico and Caribbean; they probably are post-Pleistocene, and probably accumulated in water 20-50 fathoms deep. A new cheilostome genus, Lagenicella and two new species, Reptadeonella hastingsae and Parasmittina anderseni are described, and the new family name Cleidochasmatidae is substituted for Hippoporinidae Bassler.

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