42 Bulletin io 336 



Test rounded, both sides equally compressed, peripheral margin 

 obliquely rounded, becoming somewhat lobulated near the ulti- 

 mate chamber; segments triangular, ten in the last volution, 

 separated by straight, slightly depressed septal lines which are in 

 the shape of bridges marking the retral process of the shell; um- 

 bilicus very slightly depressed, septal plane nearly round, aperture in 

 the form of a series of pores or openings along the inner margin 

 of the ultimate segment. 



Diameter, 0.26--0.78 mm. 



Horipjon and locality. — Pleistocene; Cornfield Harbor. Md. 



Geological distribution. — This beautiful little Polystomella of 

 variable size is the most abundant species in the Pleistocene 

 deposit at Cornfield Harbor. 



Genus AMPHISTEGINA d'Orbigny. 

 Amphistegina lessonii. 



Sjm. Amphistegina lessonii d'Orbigny, (parte) Ann. Sci. Nat., vol. vii. 

 p. 304, No. 3, pi. xvii,figs. 1--4, 1826. 

 Amphistegina lessonii Brady, Clial. Rept., vol. ix, p. 740, pi. cxii, 



figs. 1—7, 1884. 

 Amphistegina lessonii Bagg, Johns Hopkins Univ. Circulars, 

 vol XV, p. 5, 1895. 

 Test circular, compressed, transverse se(5lion elliptical; super- 

 ior side only slightly more elevated than the inferior; superior 

 surface shows about eighteen angular segments; inferior surface 

 less distindlly chambered, more irregular; chambers narrow, 

 angular, visible in transmitted light; surface smooth, of a brown- 

 ish yellow color. 



Diameter, 1.47--2 mm. 



According to Professor Brady this species shows great variation 

 in the amount of convexity. Our specimens agree more closely 

 with his figure 4 of plate cvi, in the Challenger Report and 

 may be considered typical for the species. 



This is not a common form and only three specimens have been 

 obtained on Potomac creek, and onl}' a few are found in the 

 Miocene of Darlington, nearly all of which are broken. 



Horizon and locality. — Eocene; Woodstock, Va. : Miocene; 

 Darlington, S. C. 



Geological distribution. — Eocene to Recent. 



