Marylaxd Geological Survey 435 



less distinct anteriorly. Umbo quite elevated, beak small, incurved over 

 dorsal valve. Dorsal valve convex on sides, having a deep mesial sinus 

 which begins at beak and broadens toward front. Surface of ventral valve 

 bearing in center a small plication which extends only part way to umbo ; 

 five plications occur on each side, those next center being stronger and 

 elevated. Dorsal valve bearing one or two short median plications and 

 about five stronger plications on each side. 



Length 4 mm. ; width 4 mm. 



This small shell closely resembles A. concava of the New Scotland, but 

 differs in its more ovate shape. The differences, however, are hardly more 

 than varietal. 



Occurrence. — Helderbekg Formation, Keyser Mejiber. Tonoloway, 

 227 feet above base of formation. 



Collection. — Maryland Geological Survey. 



[Swartz.] 

 Anoplotheca equisthiata n. sp. 

 Plate LXXIII, Figs. 22, 23 



Description. — This species resembles young or small A. flahellites. but 

 differs in having a concave dorsal valve and no fold or sinus on either shell. 

 Each valve has from eleven to thirteen simple, equal, subangular plica- 

 tions. The interspaces are as wide as the plications. 



Length 8 mm. ; width of the largest example 9 mm. 



Occurrence. — Oriskany Formation, Eidgely Member. Cumberland. 



Collection. — George M. Eoeder. 



Anoplotheca dichotoma (Hall) 

 Plate LXXIII, Figs. 24-26 



Leptocoelia dichotoma Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 452, pi. ciii6, 



figs. Za-Zc. 

 Leptocalia dichotoma Hall and Clarke, 1893, ibidem, vol. viii, pt. ii, p. 137. 

 Anoplotheca dichotoma Schuchert, 3,897, Bull. U. S. Geol. Surv., No. 87, p. 



144. 

 Cwlospira dichotoma Clarke, 1900, Mem. N. Y. State Mus., vol. iii. No. 3, p. 



42, pi. v, figs. 27-32. 

 Anoplotheca dichotoma Weller, 1903, Geol. Surv. N. J., Pal., vol. iii, p. 358, pi. 



xllx, figs. 3-6. 



