Maryland Geological Survey 241 



seem to me like an accelerated derivative from pcrplana in which the 

 adidt coarse concentric lamellae of P. perplana appear early and become 

 accentuated by the time adult conditions are reached in this specimen. I 

 think you are safe in giving it a varietal name. It corresponds closely 

 with no species I know." 



Length, 23| mm.; height, 15^ mm. 



Occurrence. — Eomxey Formation, Hamilton Member. Evitts 

 Creek below Wolfe Mill. 



Collection. — Maryland Geological Survey. 



Palaeoxeilo emarginata (Conrad) 

 Plate XXVIT, Figs. l-Ci 



Nuculites emarginata Conrad, 1841, GeoL Surv. N. Y., An. Rep., p. 50. 

 Palaeoneilo emarginata Hall, 1870, Prelim. Notice Lamellibranchiata 2, p. 7. 

 Palaeoneilo emarginata Hall, 1885, Pal. N. Y., vol. v, pt. 1, Lamellibranchiata 



ii, p. 338, pi. 1, figs. 1-11. 

 Palaeoneilo emarginata Clarke, 1903, N. Y. State Mus., Bull. 65, p. 475. 

 Palaeoneilo emarginata Grabau and Shlmer, 1909, N. Am. Index Fossils, vol. 



i, p. 400, figs. 510m-p. 



Description. — "Shell of medium size or larger, subelliptical ; length 

 usually more than twice the height; basal margin gently curving or nearly 

 straight from the post-inferior angle to the anterior end, where it is 

 more abruptly rounded; posterior margin deeply sinuate; anterior end 

 regularly and somewhat abruptly rounded ; cardinal line gently arcuate. 

 Valves regularly convex in the lower anterior half, becoming gibbous 

 above ; beaks at a little less than the anterior third from the end ; xmibonal 

 slope marked by a strong elevation or ridge, with a depression above it, 

 which produces a marked emargination ; the post-cardinal extremity, above 

 this, is produced into a linguiform extension, which is sometimes angular, 

 but usually abruptly rounded at the termination. Surface marked by 

 strong, elevated, distant, lamellose, concentric ridges, extending the entire 

 length of the shell, between which are very fine concentric striae; the 

 intermediate striae become obscure or obsolete, according to the degree 

 of weathering and nature of the matrix." Hall, 1885. 

 16 



