248 SYSTEMATIC PALEONTOLOGY 



PoLYMOEPHiXA GiBBA (d'Orbigny). 

 Plate LXIII, Fig. 12. 



Olobnlina gibba d'Orbigny, 1846, Foram. Fossiles Vienne, p. 227, pL xiii, figs. 13, 14. 

 Polymorphina gibba Brady, 1884, Chal. Kept., vol. ix, p. .561, pi. Ixxi, fig. 12. 

 Polymorphina gibba Bagg, 1896, Bull. 141, U. S. Geol. Survey, p. 92. 

 Polymorphina gibba Bagg, 1898, Bull. Amer. Pal., No. 10, p. 30. 



Description. — Test subglobular, apex slightly produced; base obtusely 

 rounded; consisting of from two to four chambers compactl}^ joined and 

 overlapping. The surface is smooth and unmarked by septal constric- 

 tions. Septa visible as delicate, oblique lines; transverse section nearly 

 circular; aperture mammiUate; length of our specimens, 0.35 mm.; 

 breadth, 0.30 mm. 



This is not a common species in the Eocene but the specimens are 

 very similar to those from the Navesink formation (Lower Marl Bed) of 

 the New Jersey Cretaceous. 



This form is very similar to Polymorphina ladea from which it is 

 with difficulty separated. Its distribution is probably the same, both 

 recent and fossil. 



Occurrence. — ISTanjemoy Formation. Woodstock. Aquia Forma- 

 tion. Upper Marlboro, Brooks Estate near Seat Pleasant. 



Collections. — -Johns Hopkins University, Maryland Geological Survey. 



Polymorphina lactea (Walker and Jacob). 

 Plate LXIII, Fig. 18. 



Serpula lactea Walker and Jacob, 1798, Adam's Essays (Kanmacher's Edit.) p. 634, 



pi. xxiv, fig. 4. 

 Polymorphina lactea Williiimson, 1858, Recent Foram. Gt. Brit., p. 71, pi. vi, fig. 147. 

 Polymorphina lactea Brady, Parker and Jones, 1870, Trans. Linn. Soc. London, vol. 



xxvii, p. 213, pi. xxxix, fig. 1, a-c. 



Description. — Test ovate or subpyriform, only slightly depressed, con- 

 sisting of three or four chambers with flush sutures and scarcely distinct 

 septal lines; aperture terminal, radiate; diameter, 0.39 mm. (Miocene). 



It is, as pointed out above, very difficult to separate this form from 

 P. gihha. It is somewhat more graceful and slender and less obtuse and 

 the writer believes that there is less good ground for separating these 

 two forms than for distinguishing Polymorpliina communis and Poly- 



