Markings angular, decreasing slightly toward the coarsely striated border, covered with fine puncta.
Markings rounded, large, decreasing toward the broad border, which is coarsely marked with distant striæ. The cells are punctate.
In the fossil forms the puncta are not evident, hence the species is usually described as not punctate.
Markings polygonal, slightly decreasing toward the border where they are much smaller; border well marked, striate. Quite variable in size.
Common in the blue clay and along the coast.
Pl. 3, Fig. 11. Fig. 1 is probably a smaller form.
COSCINODISCUS SUBAULACODISCOIDALIS RATTR.
Markings small, decreasing toward the border in somewhat fasciculate rows. About one-third the distance from the border are five (Rattray finds six) well-marked apiculi somewhat resembling those of Aulacodiscus. Border narrow, hyaline.
Rare in the lower stratum of the blue clay.
Markings angular with central dots, increasing from the centre toward the border, where they are smaller.
Central space and rosette absent, markings large, angular, not punctate, with large central papillæ, decreasing toward the border. Border wide, coarsely marked with rows of granules, and with two indentations on the inner side distant from each other about two-thirds of the diameter.
Distinguished from Coscinodiscus asteromphalus var. omphalantha Grun., which also has two constrictions, by the absence of punctate markings.
Central space small, surrounded by a rosette of large polygonal cells from which radiate hexagonal cells, increasing about half way toward the border and then slightly decreasing. Cells punctate.
COSCINODISCUS ASTEROMPHALUS VAR. OMPHALANTHA (EHR.) GRUN.
Central space absent, rosette evident. Markings 2½ in 10 µ, somewhat smaller near the rosette and decreasing near the border, which is constricted in two places, as in C. biangulatus.
Central space and rosette distinct; markings polygonal, not punctate, with large papillæ, smaller near the rosette, increasing toward the semi-radius, and then decreasing to the striated border which is comparatively narrow.
Valves elliptical, major axis a little more than twice the minor. From a point, usually near one side, radiate rows of granules in lines nearly parallel to the major axis. Border broad, with distinct striæ.