Blue clay and along the coast. Very common in the water supply of Philadelphia and Camden, where the diameter seldom exceeds 40 µ and the markings on the semi-radius are 10 in 10 µ.
Pl. [2], Fig. 17.
COSCINODISCUS DENARIUS SCHMIDT
Markings larger than in C. subtilis, equal, forming usually ten fasciculi, each beginning near the semi-radius and containing ten parallel rows of granules.
Common in the blue clay and sparingly along the coast.
Pl. [2], Fig. 13.
Forms are found intermediate between C. subtilis and C. denarius, as shown in Fig. 15.
COSCINODISCUS POLYACANTHUS GRUN.
Markings angular, 10 in 10 µ, decreasing toward the border, fasciculate. Apiculi large, twelve or more, usually inserted at the middle of each fasciculus, and extending into the interior of the cell. The apiculi in outline resemble the heads of horse-shoe nails, and are seen with difficulty except when the valve is examined from the inner side. Border narrow, striated. Diam. 70 µ.
Pensauken, N. J., artesian well.