352 SYSTEMATIC PALEONTOLOGY 



Shell rather thick and solid, especially in the umbonal region; car- 

 dinal teeth well developed; margin creniilated or smooth. 



Length, 22 mm.; height, 19 mm.; diameter. G mm. 



Occurrence. -Calveet Formatiox. Plum Point, Lyon's Creek (rare). 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Academy of Natural Sciences of Philadelphia. 



x^starte calvertensis n. sp. 

 Plate XCIV, Figs. 3, 4. 



Astarte calvertensis (Glenn) Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, jit. vi, 

 pp. 1492, 1494 (listed). 



Description. — Triangular; shell nearly flat, with about forty-five regu- 

 lar, nearly equal concentric lines; apex moderately prominent, right 

 angled or obtuse; anterior side shorter than posterior; lunule not deeply 

 excavated; anterior basal margin a well rounded curve, posterior basal 

 margin straight or slightly emarginate; posterior extremity above the 

 line of the base and sharply rounded; posterior side straight; ligament 

 areas impressed; teeth moderately prominent; basal margin crenate or 

 smooth. 



This species differs from A. hella, A. concentrica and A. compsonema 

 (all three synonymous?) to which it seems most closely related by being 

 thinner, much flatter, less equilateral, more emarginate posteriorly and 

 with less prominent and less projecting beaks. 



Length, 25 mm.; height, 20 mm.; diameter, 4.5 mm. 



Occurrence. — Calvert Formation. Plum Point. 



Collection. — Maryland Geological Survey. 



Astarte symmetrica Conrad. 



Astarte symmetrica Conrad, 1834, Jour. Acad. Nat. Sci. Phila., vol. vii, 1st ser. 



p. 134. 

 Astarte symmetrica Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, pt. vi, p. 1488. 



Description. — This species has not been found by the author among 

 Maryland materials. 



Occurrence. — St. Mary's Formation (?). St. Mary's Eiver. 

 Collection. — U. S. National Museum. 



