Maryland Geological Survey 459 



ACTINOPTERIA RETICULATA Weller 



Plate LXXVI, Fig. 6 

 Actinopteria reticulata Weller, 1903, Pal. N. J., vol. iii, p. 245, pi. xxii, fig. 3. 



Description. — " Left valve large, subrhomboidal in outline ; the body 

 subovate, with an obliquity of 27° between the hinge-line and the umbonal 

 ridge; beak but slightly elevated above the hinge-line. Anterior margin 

 nearly straight or slightly sinuate, forming a rounded angle of about 80° 

 with the hinge-line; basal margin regularly curved; posteriorly it 

 rounds more abruptly into the nearly straight or slightly sinuate posterior 

 margin which is nearly parallel with the anterior margin. Posterior wing 

 large, slightly convex, limited below by a moderately distinct, rounded 

 sinus; the posterior cardinal extremity obtuse. The body of the shell is 

 marked by conspicuous, concentric lines of growth and by more or less 

 discontinuous, radiating costs. Near the margin of the shell the con- 

 centric lines are more crowded and the radiating costge are less con- 

 spicuous, but on the upper portion of the shell the two sets of markings 

 give to the surface a nodose appearance. The posterior wing is marked 

 like the body of the shell, but the radiating markings are much less con- 

 spicuous. Eight valve unknown. 



" The dimensions of the type specimen are : Height 35 mm. ; oblique 

 length from beak to postero-basal extremity 48 mm. ; length of hinge-line 

 29 mm." Weller, 1903. 



The individual specimen at hand is badly broken and consists of only 

 one valve. The general character of the shell agrees with this species and 

 the body of the shell is marked by conspicuous concentric lines of growth 

 and by more or less discontinuous radiating costas. There is little doubt 

 as to the identification, although the individual is only in part preserved. 



Occurrence. — Helderberg Formatiox, Keyser ]\[ember. Keyser, 

 West Virginia. 



Collection. — U. S. Xntional ^Museum. 



[Maynard.] 



