256 DISCOVERY REPORTS 



Genus Schimperiella Karsten 

 Karsten, 1905 



Schimperiella antarctica Karsten. 

 Karsten, 1905, p. 88, pi. 8, fig. 6. 



Cells discoid, solitary, small. Valves convex, dissimilar. The upper valve is surrounded 

 with a wide, flat margin, radially striate. The central portion is convex and covered with 

 puncta arranged irregularly in sectors or whirls. Small central hyaline area present. 

 Puncta smaller and more dense towards the margin. The lower valve possesses no striate 

 flattened margin, but is uniformly convex throughout, and is furnished with puncta 

 arranged in radial lines. The extreme margin of the lower valve is surrounded with a 

 line of spinulae. Diameter of valve 48/u, ; pervalvar axis 12-15/*. 



The genus Schimperiella is a small one, having its distribution in the Antarctic only. 

 It is characterized by a peculiar form of dimorphism in the valves. It is probably closely 

 allied to many of the Antarctic forms of Actinocyclas, wherein the same type of di- 

 morphism is noticed frequently. Probably a neritic species only, but it is likely that it 

 spends part of its time as a bottom form. 



Observed at St. 475. 



Schimperiella valdiviae Karsten. 

 Karsten, 1905, p. 88, pi. 8, fig. 7. 



Cells discoid, solitary, small. Valves convex, dissimilar. The upper valve is surrounded 

 with a strong and usually wide, flat margin, radially striate. The central portion is con- 

 vex, and covered with striae, striae moniliform, radial. Small central hyaline area pre- 

 sent. Puncta increase in size slightly and become more dense as they approach the 

 margin. Lower valve also surrounded by a narrow margin, margin radially striate. The 

 central area of the valve is convex and covered with small hexagonal areolation, areola- 

 tion entire, no central hyaline area, and no central rosette. Areoles arranged in irregular 

 tangential lines decreasing in size slightly as they proceed to the margin. Apiculi and 

 spinulae absent. Diameter of valve 28-34/M. 



A small neritic species having the same distribution as S. antarctica. 



Observed at St. 461. 



Genus Charcotia M. Peragallo 

 Peragallo, M., 1921 



Charcotia bifrons (Castracane) M. Peragallo. (PI. X, figs. 6, 7.) 



Peragallo, M., 1921, p. 78. 



Coscinoducus bifrons Castracane, 1886, p. 156. 



Charcotia Janus var. plana M. Peragallo, 1921, p. 78. 



Cells discoid, small. Valves flat or nearly so. Valves dissimilar. The valve surface of 

 both the upper and the lower valve is very finely marked with exceedingly faint radial 

 striation. Upon the upper valve the central area is furnished with a small irregular ring 



