328 SYSTEMATIC PALEONTOLOGY 



sides and ends forming with the base regular curves; anterior end more 

 acutely rounded and narrower than posterior one; lateral lamellae short, 

 strong and standing out from the hinge area well into the interior of 

 the shell; lateral grooves short and deep; ligament impressions high up 

 and elongated, the posterior being the larger and broader; pallial line 

 indistinct; outer surface with light, uneven concentric lines and here 

 and there a deeper, stronger groove marking, perhaps, a resting stage. 



Length, 4.5 mm.; height, 3.8 mm.; diameter, 0.9 mm. ' 



Occurrence. — Calvekt Formation. Plum Point. 



Collection. — Maryland Geological Survey. 



Erycina marylandica n. sp. 

 Plate LXXXVIII, Figs. 1, 2, 3. 



Description. — Shell small, ovate, depressed, beak very low; anterior 

 and posterior sides straight near the beak and meeting in an angle there; 

 anterior end regularly rounded; posterior end blunted; base regularly 

 arched; lateral lamella distinct, rather long; posterior adductor scar 

 rounded and not so high up as the narrower, elongated anterior one; 

 pallial line well away from the margin; outer surface with irregular, con- 

 centric grooves or undulations here and there stronger than elsewhere. 



Length, 3.9 mm.; height, 3.1 mm.; diameter, 0.9 mm. 



Occurrence. — Calvert Formation. 3 miles south of Chesapeake 

 Beach, Plum Point. 



Collection. — Maryland Geological Survey. 



Erycina rickardia n. sp. 



Plate LXXXVIII, Figs. 4a, 4b. 



Description. — Shell ovate-quadrate, thick, depressed; beak low but 

 projecting slightly; very inequilateral, the anterior side being much the 

 longer; anterior side concave near the beak; anterior end bluntly 

 rounded, its curve being continuous with the base; posterior side and 

 end a regular curve meeting the base at an angle and on a line with 

 the base lateral laminae and grooves quite prominent; adductor scars 

 distinct, the anterior one the higher up; pallial line rather broad and 



