436 Systematic Paleontology 



Description. — " Shell oval ovate, concavo-convex. Ventral valve arcvi- 

 ate, strongly convex, or approaching to subcarinate in the middle and 

 abniptly sloping at the sides ; beak incurved. Dorsal valve concave, more 

 abruptly depressed in the center, and flattened on the cardino-lateral 

 margins. Surface marked by dichotomizing plications ; the central one of 

 the dorsal valve becoming tripartite, and the three lateral ones, which are 

 simple at the origin, bifurcating and making six at the margin of the 

 shell : on the ventral valve there are two smaller plications in the center, 

 and four dichotomizing ones on each side ; concentrically marked by a few 

 imbricating lines of growth." Hall, 1859. 



This species is the Oriskany continuation of A. concava of the Helder- 

 berg, but is readily distinguished from it by the greater size which is from 

 two to three times larger, the greater number of plications and the less 

 concave dorsal valve. The plications are not always decidedly dichot- 

 omous, some specimens having them quite regular, as in A. concava. 



Length and width about 10 mm. 



Occurrence. — Oriskany Formation, Eidgely Member. North 

 Branch. 



Collections. — ^]\Iaryland Geological Survey, American Museum of 

 Natural History, U. S. National Museum. 



Subgenus LEPTOCCELIA Hall 



Anoplotheca (Leptoccelia) eimbriata (Hall) 

 Plate LXXIII, Figs. 27, 28 



Leptoccelia fimbriata Hall, 1859, Twelfth Ann. Kept. N. Y. State Cab. Nat. 



Hist., text fig. 3, p. 33. 

 Leptoccelia fimbriata Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 450, pi. ciii&. 



figs. 2a-2f. 

 Leptoccelia flmhriata Hall and Clarke, 1893, ibidem, vol. viii, pt. ii, p. 137, 



pi. liii, figs. 47-52, 54, 55. 



Description. — " Shell small, longitudinally semielliptical, the length 

 less than the width. Ventral valve convex, more elevated along the 

 middle, declining regularly at the sides, the cardinal angles somewhat 

 compressed : beak small, little elevated above the cardinal line and slightly 

 incurved, with a minute rounded foramen at the extremity, the lower side 



