SIAUVI.AM) CKdl.OGICAL SL'KVKY 193 



SubgeiuiN CKVl'IIAIiOSTREA floncni. 

 OSTREA (GRVrUAKOSTltEA) VOilEU (Mcjrtoil). 



rialc L. Fius. 1. la, 11), 2. ;5. I. la, r>. 



Oryp/iaea rumcr .Murtuii, ISIiU, Jour. Acad. Nut. Sci. I'liila., vol. vi (1st series), p. 83. 



(rri/phaea vomer Morton, 1834, Syn. Org. Rem. Cretaceous, p. 54, pl.ix, fig. 5. 



Gnjphaea vomer Conrad, 1835, Trans. Geol. Soc. Peiin., vol. i, p. 330. 



Gnjphaea vomer Conrad, 184'i, Proc. Nat. Inst., Bull, ii, p. \'>:l. 



Oxtrvii (Oryiihiuoxtrva) xiihcrcrmi ('()iira<l, isCi.'), Aiiht. Joui'. ('oncli., vol. i, ]>. 1.5 



(name only). 

 Oxtrca sp. Clark, 181t5, Johns Hopkins Univ. Circ, vol. xv, p. 0. 

 Ostrea sp. Clark, 18110, Bull. 141, U. S. (ieol. Survey, p. 88, pi. xxxix, li-rs. 3«-3r. 

 O.ilrea mbeversa Clark, 1896, Bull. 141, U. S. Geol. Survey, i'. 'X',. 

 Ostrea {Gryphaeontrea) subeversa Dall, 1898, Trans. Wagner Free lust. Sci., vol. iii, 



pt. iv, p. 681. 



Description. — " Oblong-oval, thin, narrow; lower valve deep, longi- 

 tncJinally curved; beak prominent, curved laterally; upper valve small in 

 proportion to the lower, and marked with distinct, concentric, squamose 

 plates." Morton, 183-i. 



The possible equivalence of this form with Grypliaea vomer Morton, 

 or Grypliaea eversa Mellville was suggested by Dall. Conrad recorded 

 the species from Piscataway and Upper Marlboro. 



Length, 39 mm.; width, 20 mm.; depth of lower valve. 10 mm. 



Occurrence. — Naxjemoy For:hatiox. ^ mile below Chapel Point. 

 Aquia Formation. Piscataway, Upper Marlboro, Aquia Creek, Po- 

 tomac Creek, 2 miles below Potomac Creek, Sheckel's Farm near South 

 River, Fredericktown, Glymont. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Philadelphia Academy of Xatural Sciences. 



Genus GRYPHAEA Lamarck. 



Gryphaea tesicularis Lamarck. 



Plate L, Figs. 6, 6a. 



Gryphaea vesicularis Lamarck, 1806, Ann. ilus. viii, p. 160, pi. xxii, tig-. 3. An. 

 Sans. Vert., vol. vi, p. 209. 



A single specimen of this form was found associated with Eocene 

 fossils at Clifton Beach. It is very perfect, having both valves in posi- 

 tion. It seems hardly possible, however, that it can be a representative 

 13 



