Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/155

1872.] JONES AND PARKER— CRETACEOUS FORAMINIFERA. 121 fails to present some variety or subvariety of Pulv. repanda. Of the Pulv.-Menardii group there are representatives in Nos. 1, 4 5, 6, 7, 9, 10, 12, 13, 15, 16, 19, and 20. Of the elgans group there are abundant and strongly marked forms in relatively few strata ; and all but one of them are very close to, indeed scarcely separable from, the typical elegans, except by the comparative richness of the shell-growth. Columns 1, 2, 3, 8, 11, and 18 (?) have Pulv. elegans or some of its subvarieties ; and its greatest abundance is decidedly with the Lower Cretaceous rocks. A very few Pulvinulinoe of the Schreibersii group are scattered here and there through the series — columns 4, 8, and 17.

Rotalia is represented by one variety of R. Beccarii, namely R. exsculpta, in columns 8 and 16, and far more persistently by the deep-sea variety R. umbilicata in Nos. 2, 8, 9, 10, 11, 12, 13, and 19.

All these typical species, and several of their varietal forms, have continued through the Tertiary period on to our own times, and are to be found in some existing sea or ocean. The chief distinction between the Cretaceous Rotalines and those of the present day is, that a vast number of varietal forms, which have sprung up during the intervening ages, indicate, by their multiplicity, the varying conditions of successive and changing marine areas, with differing limits, depths, and climates.

This is shown in Table II. (p. 123), by which we follow, though with unequal steps, the progressive development of the several types, as far as the materials before us will serve.

Thus the " conical" Planorbulinoe began early ; they are present in the Lower Cretaceous deposits; they abound in the White Chalk, the Tertiary beds, and the Atlantic. Pl. Ungeriana is the most persistent form. The " nautiloid " or Anomaline Planorbulinoe abound in both the Lower and the Upper Cretaceous formations, and in the Tertiaries ; but they are not so predominating in the Atlantic. Pl. ammonoides is the leading and lasting form. On the other hand, the " plano-convex" or Truncatuline Planorbulinoe have flourished freely throughout and nearly everywhere, in some subvariety or other of Truncatulina lobatula. The orbicular, concentric, plano-convex Pl. mediterranensis (vulgaris) is a later form ; and its annular growth indicates a morphological position higher than that of its simply coiled allies.

Pulvinulina repanda (proper) is represented in the Chalk of Maestricht, but in none of the other Cretaceous beds. It is rare in the Tertiaries of our Table (occurring only in the Pliocene), but is scattered throughout the Atlantic. P. auricula existed in the Nummulitic sea, abounded in the mid-Tertiary times, and, living now, is abundant in some places ; but it is wanting in the Chalk. P. Menardii, however, was one of the early representatives of the genus. In New Jersey (North America) it occurs in the Greensand. With us it begins with the White Chalk, and has continued with increased prolificness till now. P. Schreibersii occurs sporadically in the Greensand of New Jersey, the Chalk-formations of Eastern Europe, the