EAST AMERICAN SCAPHOPOD MOLLUSKS. 



73 



The type, Cat. No. 68117, U.S.N.M., was collected by Commander 

 Rush United States Navy, in Turtle Harbor, Florida, in 4 fathoms. 



Specimens from off Cape Fear and Frying Pan Shoals are in the 

 Philadelphia Academy of Sciences collection. The most southern 

 record is of specimens from Barbados, in the State University of 

 Iowa collection. It is a species of very shallow water range. 



The lots in the museum collection are as follows : 



1 Type. 



Subgenus LAEVIDENTALIUM Cossman, 1888. 



1888. Laevidentalium Cossman, Ann. de la Soc. Royal de Malac. de Belgique, 



vol. 25, p. 9. 

 1897. Laevidentalium, Pilsbry and .Sharp, Tryon's Manual of Conchology, vol. 



17, p. 97. 



Shell smooth or showing growth lines only; wholly without longi- 

 tudinal sculpture. Slightly oval or round section. The apex is 

 simple, as defined by Cossman, or with Antalis-like notch on the 

 convex side, as expanded by Pilsbry and Sharp. 



Cossman's subgenus was created for a fossil group of smooth shells 

 showing no apical features. Pilsbry and Sharp are fuUy justified in 

 including certain recent species showing the conventional apical 

 features of Antalis. The essence of the characters for the group lies 

 in the whoUy sculptureless shell which is even smooth on the tip. 



KEY TO THE SPECIES OF THE SUBGENUS LAEVIDENTALIUM. 



Very strongly curved callipeplum, page 74. 



Not very strongly curved. • 



Shell slender. 



Very long (over 50 mm.) perlongurn, page 75. 



Not very long (under 50 mm.) liodon, page 76. 



Apical notch on convex side liodon liodon, page 76. 



Apical notch on concave side liodon alloschismum, page 77. 



