246 SYSTEMATIC PALEONTOLOGY 



valve moderately convex on the umbo, but more flattened towards the 

 cardinal extremities; cardinal area narrow, concave above; beak project- 

 ing slightly beyond the cardinal margin. Surface marked by about 50 

 fine, subequal, radiating costae, increasing by bifurcation. 



The numerous fine radiating costae distinguish this shell from the 

 closely allied Dalmanella wemplei Cleland, which differs in having larger 

 costae at regular intervals. 



Occurrence. BEEKMANTOWN LIMESTONE (Ceratopea zone). West of 

 Hagerstown, near Halfway, and east of Williamsport, Maryland. 



Canadian at Point Levis, Quebec, Newfoundland, New Brunswick, 

 New Jersey and Pennsylvania. 



Collections. Maryland Geological Survey, U. S. National Museum. 



DALMANELLA WEMPLEI Cleland 

 Plate XXXI, Figs. 7-12 



Dalmanella (Orthis) wemplei Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 129 



(257), pi. xvii, figs. 10-13. 

 Dalmanella wemplei Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, 



p. 124, pi. iv, figs. 10-12. 

 Dalmanella wemplei Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 19. 



Description,. Shell small, the average being about 5 mm. long and 

 6 mm. wide, subquadrangular to subcircular in outline, with the hinge- 

 line slightly shorter than the width; cardinal extremities usually quite 

 angular. Pedicle valve strongly convex, highest posterior to the middle ; 

 beak elevated, projecting beyond the hinge-line; cardinal area high, 

 slightly arched. Brachial valve much less convex than the pedicle, with 

 a mesial depression which may become a shallow sinus towards the front. 

 Surface of each valve marked by from 10 to 16 stronger, radiating costae, 

 alternating with from two to four finer ones. 



This species differs from the closely related Dalmanella electra (Bill- 

 ings) which occurs in the higher beds of the Beekmantown, especially 

 in its coarser striae which alternate with from two to four finer ones. 



The original types were collected in the Tribes Hill limestone at Fort 

 Hunter, New York. The species has been identified by Weller in the 



