MARYLAND GEOLOGICAL SURVEY 733 



and regularly overlapping ; ligament obsolete ; hinge margin reflected, 

 edentulous; produced under the umbones into a minute linguiform 

 process for the support of the pedal muscle ; characters of interior obscure ; 

 tubes compressed, corrugated, lenticular in cross-section. 



Dimensions. Altitude 5 mm., latitude 3.2 mm., maximum diameter 

 4 mm. 



The valves are separated from those of the co-existent Teredo irregularis 

 Gabb by the non-lobate posterior dorsal extremity, while the tubes differ 

 from the irregular cylindrical tubes of Gabb's species in being compressed 

 and corrugated. 



Occurrence. MoNMOUTH FORMATION. Brightseat, Prince George's 

 County. 



Collection. Maryland Geological Survey. 



