Sabine Lake is a lake estuary in the extreme south eastern corner of Texas. Field data were obtained from the present-day surface and from depths up to 9 ft. below the surface through the use of a coring device. Rangia cuneata Gray is an estuarine genus and occurs in Sabine Lake mainly N. of 29 degrees 50'N. It occupies the fresher portion of the lake and could be used as an index for this biotope. Shells generally occur as scattered individuals. Crassostrea virginica (Gmelin) occurs singly or in reefs S. of 29 degrees 50'N. This species serves as an index for the more saline portion of the lake. The pattern of core spacing was too widespread to delineate the geometry of occurrence of either form.