The Anadarid Subgenus Caloosarca in the Western Atlantic Region

Abstract

Species referable to the anadarid subgenus Caloosarca Olsson, 1961, are distinguished by their broadly elongate valves with anteriorly located umbos and, especially in the younger stages of growth, a broadly emarginated posterior end that gives the valves an auriculate or winged outline. The ligament in the young and early mature stages is confined to the posterior portion of the cardinal area, extending anteriorly only to a point directly below the umbo, with the anterior portion of the area bare; in late mature and gerontic stages this anterior portion may also be covered. The teeth on the hinge plate are in two series that meet immediately below a transverse groove on the cardinal plate which marks the anterior end of the normal ligamental structure. Seven named species, differentiated primarily upon the number and nature of the radial ribs that ornament the valves, are recognized. A probable eighth species is represented by specimens dredged from upper Miocene deposits in the bed of the Caloosahatchee River, near Olga, lee County, Florida, but present material is inadequate for description. One species, Anadara (Caloosarca) notabilis (Roding), is living in relatively shallow waters from Florida to southern Brazil and has been reported from Pleistocene deposits from Cape Hatteras to Brazil. The other species are known only from the fossil record, with five of them being confined, so far as is presently known, to peninsular Florida. Two new species, A. (C.). nota florida and A. (C.) boerleae, are described from the upper Miocene, Pinecrest Formation; one species, A. (C.) crassicosta (H eilprin) occurs in the Pliocene, Caloosahatchee Formation; and two species, A. (C.) aequalitas (Tucker and Wilson) and A. (C.) catasarca (Dall), are confined to deposits referred to "Unit A" of Olsson and Petit, 1964, an as yet unnamed post-Caloosahatchee formation. The type of the subgenus, A. (C.) rustica (Tuomey and Holmes) is known only from the Pliocene, Waccamaw Formation of South Carolina and adjacent areas of southern North Carolina.