Pl. [38], Fig. 5.
Rattray's description of C. polyacanthus var. intermedia Grun., from Cape Wankarema, Siberia, gives the diam. as 60 µ, and there are about 7 markings by actual count in 10 µ in Grunow's figure (Diat. Fr. Jos. Land, Pl. 3 (C), Fig. 25). The apiculi are more numerous, but there appears to be little doubt of the general similarity. The Philadelphia form is abundant in the Pensauken well deposit at a depth of 33 ft. The apiculi become quite distinct in slides stained with silver nitrate by Mr. F. J. Keeley; they are distinct from small apiculi sometimes evident between the fasciculi. The specimens in the Pensauken deposit are mingled with other forms which cannot be distinguished from C. subtilis. Whether the two are identical, I am unable to determine. Rattray (Rev. Cos., p. 47) refers to H. L. Smith's Type Slide No. 100, from rice-field mud, Savannah, Ga., as C. subtilis. In Smith's slide, in my possession, a number of the forms show faint outlines of the large apiculi and are otherwise exactly like C. polyacanthus.
RADIATI
COSCINODISCUS VELATUS EHR.
Markings angular, decreasing slightly toward the coarsely striated border, covered with fine puncta.
Blue clay.
Pl. [3], Fig. 2.
COSCINODISCUS MARGINATUS EHR.
Markings rounded, large, decreasing toward the broad border, which is coarsely marked with distant striæ. The cells are punctate.
Common in the blue clay.