Maryland Geological Survey 269 



the shell, frequently becoiniiig nearly obsolete on the umbonal region.'' 

 Hall, 1885. 



This species as compared with AJ. concentnca occurs in the bluer and 

 more argillaceous Hamilton shales of Maryland. It is a well marked 

 species and differs from the other Modiomorphas found in Maryland in the 

 more nearly parallel cardinal and basal margins; well marked, angular 

 umbonal ridge; subtruncate posterior end; and the obsolescence of the 

 striae on the umbonal region. The small specimen repi'esented by figure 5 

 was thought at first to show very imperfectly preserved fine striae on the 

 posterior portion of the shell and for this reason it was referred to 

 Modiella pygmaea (Conrad). Further study, however, taking more 

 account of its form leads me to conclude that it is a young specimen of 

 Modiomorpha subalata (Conrad), still younger than the one represented 

 by fig. 1, pi. xxxix, Lamellibranchiata ii, vol. v, pt. i. Paleontology of 

 New York. The specimen was submitted to Dr. Grabau with the above 

 opinion who wrote me as follows : " You are right I think. I should 

 call it young M. subalata. The form hardly warrants reference to 

 Modiella." 



Length, 25-35 mm.; height, 15-20 mm. 



Occurrence. — Romney Formation", Onondaga ]\Iember. Williams 

 Eoad 3^ miles southeast of Cumberland ( ?). Hamilton Member. East 

 bank Evitts Creek below Wolfe Mill. 



Collections. — Maryland Geological Survey; ]^ew York State Museum; 

 American Museum of Natural History. 



Modiomorpha mytiloides (Conrad) (?) 

 Plate XXXIII, Fig. 7 



Cypricardites mytiloides Conrad, 1841, GeoL Surv. N. Y., 5th An. Rep., p. 52. 

 Modiomorpha planulata Hall, 1870, Prelim. Notice Lamellibranchiata 2, p. 74. 

 Modiomorpha mytiloides Hall, 1885, Pal. N. Y., vol. v, pt. i, Lamellibranchiata 



ii, p. 277, pi. xxxvii, fig. 3; pi. xxxviii, figs. 1-16. 

 Modiomorpha mytiloides Clarke, 1903, N. Y. State Mus., BuU. 65, p. 450. 

 Modiomorpha mytiloides Grabau and Shinier, 1909, N. Am. Index Fossils, 



vol. i, p. 514, flg. 691b. 



