Makyland Geological Survey 441 



to something over one-third the distance to the front. Just below the beak 

 it divides at the top, carrjung a small but pronounced spondylium (crural- 

 ium). The sides of the spondylium cun'e out to the margin of the shell, 

 joining it about one-half way between the elongate, narrow dental socket, 

 and the beak. 



" A characteristic pedicle valve measures : Length 25 mm. ; height 20 

 mm. ; greatest width 16.25 mm." Grabau, 1910. 



Occurrence. — Helderberg Formation, Keyser Member. Cherry Run, 

 West Virginia. 



Collection. — Maryland Geological Survey. 



[Maynard.] 



WhITFIELDELLA ( ?) NUCLEOLATA (Hall) 



Plate LXXIII, Pigs. 37-40 



Atrypa nudleolata Hall, 1852, Nat. Hist. N. Y., Pal., vol. ii, p. 328, pi. Ixxlv, 



fig. 10. 

 Merista nucleolata Hall, 1859, 12th Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 78. 

 Meristella nucleolata Whitfield, 1882, Geol. Wis., vol. iv, p. 321, pi. xxv, fig. 5. 



Description. — " Shell round oval or oval ovoid; beak of the dorsal valve 

 often much extended, and incurved over the ventral valve; surface con- 

 centrically striated ; front of the shell indented, the indentation connected 

 with a depression or groove down, the center of the dorsal valve, and some- 

 times a similar one on the lower half of the ventral valve. This species 

 approaches very closely the A. nitida of the Niagara group, but is less 

 elongated, and the identation in front and the groove down the center of 

 the dorsal valve are more conspicuous in the species from the Coralline 

 limestone. There are sometimes, however, specimens which do not possess 

 these characters, and the shell is then not easily distinguished from those 

 in the Niagara group." Hall, 1852. 



Occurrence. — Helderberg Formatiok, Keyser Member. Keyser, 

 West Virginia. 



Collection. — Robert Gordon. 



[Maynard.] 



