This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.
|Pulvinulina arca Cushman 1926|
= Globotruncana arca
|Pulvinulina arca contusa Cushman 1926|
= Contusotruncana contusa
|Pulvinulina crassata Cushman 1925|
= Morozovelloides crassatus
|not figured||Pulvinulina crassata var. densa Cushman 1925|
|Pulvinulina menardii var. fimbriata Brady 1884|
= Globorotalia menardii
|Pulvinulina menardii var. tumida Brady 1877|
= Globorotalia tumida
|Pulvinulina scitula Brady 1882|
= Globorotalia scitula
|Pulvinulina tricarinata Quereau 1893|
= Globotruncana linneiana
|Pulvinulina tumida var. flexuosa Koch 1923|
= Globorotalia flexuosa
|Pulvinulina velascoensis Cushman 1925|
= Morozovella velascoensis
External Characters and Internal Structure.—The group of Rotaline forms which are associated in this genus consists of those which accord more or less closely with its type,—the Nautilus repandus of Fichtel and Moll, the Placentula pulvinata of Lamarck, the Rotalia or Rotalina repanda of later systematists,—in the freedom of growth and in the fineness of the porosity of its shell ; by both of which characters, but especially by the second, it is distinguished from Discorbina. The shells of this genus are usually composed of from seven to twenty-six segments of variable convexity, somewhat loosely aggregated in a depressed turbinoid spire, so as to have a biconvex form with the upper side thickest, and an angular or sub-carinate margin (Fig. XXXII, A, p. 201). On the under side there is a large umbilical space, which may either remain open (ex, Fig. 102), or may be partially or completely filled by exogenous deposit. The segments usually undergo a rapid elongation; and sometimes the later ones spread themselves out irregularly (ex. Figs. 95—100). An elongation takes place in the septal plane, in accordance with the extension of the chambers ; and in such cases it tends to become flattened (ex, Fig. 95), and is very commonly punched with large " orbuline" foramina. The aperture is usually a large slit at the base of tlie umbilical margin of the septal plane ; and is frequently still further enlarged by irregular deficiencies at its septal edge. In the typical Pulvinulinae the exogenous deposit is chiefly confined to the septal bands, which it often raises into ridges so as to produce a strong "limbation;" but it may also roughen the general surface with minute granulations. Some of the most oblong-varieties, as the Rotalina oblonga of Williamson (ex, p. 51) were included by D'Orbigny in his genus Valvulina.
365. The expanded form of this type may give place to one more contracted, in which the segments are more compactly arranged, so as to produce by their aggregation a thick conical shell, of which the external walls are " flush." In this variety the upper surface usually receives a considerable amount of exogenous deposit, which forms a strong " limbation" on the septal lines (ox, Figs. 101, 103), and covers the outer walls of the chambers with large closely-set granules ; and the aperture passes into the condition of a notch. Tlie limbation and granulation attain their maximum in the conus-shaped P. caracolla of the Oolite, Gault, and Chalk-marl, in which the limbation is stronger than in any other Rotalines, the faces of the chambers often lying deep between wall-like ridges both above and below. The variety known as Rotalia menardii is a common deep-sea form of Pulvinulina, flattish, limbate, and granular; and this is sometimes accompanied by the R. elegans vel Partschiana (lxxiii), a large flush-chambered shell, with a prominent umbo formed by a mass of exogenous deposit, which variety ranges also into shallower water. In some other varieties allied to R. menardii the limbation is wanting; the septal bands being flush with the surface, or being even furrowed. In the P. Schreibersii and allied varieties the limbation is but faint, or is altogether wanting, on the upper surface of the shell; whilst on the under surface there is a strong astral limbation proceeding from the exogenous deposit which occupies the umbilical vestibule.
366. The characteristic form of Pulvinulina is subject in the Laminarian zone of warmer latitudes to a modification so remarkable, that its Rotaline character would scarcely be recognisable if its affinity were not traceable through intermediate gradations. This form (Plate XIII, figs. 4—6) has been described by D'Orbigny under the designation Planorbulina vermiculata ; but although to a certain extent analogous to Planorbulina in its plan of growth, it differs from it entirely in other characters, and can be readily shown to be essen-tially a Pulvinulina extremely flattened-out, of which the later chambers elongate themselves like the continuous tube of a Spirillina, with very few interposed septa, sometimes returning into themselves so as to form complete though irregular annuli, of which the earlier are surrounded by the later. The substance of the shell in this curious variety is very finely porous, the pores being grouped in little bundles (fig. 6), and sometimes looks almost horny in its transparency and hue ; but on its attached surface (fig. 5) we notice that it is (as it were) punched-through with large irregularly scattered apertures. These expanded forms sometimes attain a diameter of 1-7th of an inch; on the other hand, the contracted deep-sea forms have no greater a diameter than 1-250th of an inch. The diameter of the ordinary trochoid forms of moderately deep water ranges from about 1-20th to 1-50th of an inch.
367. Affinities.—This genus holds among Rotalines, in regard to the fineness of the texture of its shell, and the freedom of its mode of growth, a rank analogous to that of Bulimina in the Textularine series. Its nearest affinity, however, out of its own sub-family, is to Spirillina, to which its lowest forms approximate closely in mode of growth; whilst the large pores that are met with in the chamber-walls, not only in these but in higher forms, mark the persistence of an Orbuline condition of the animal. In this genus, moreover, as in the two preceding, we find complanate nearly symmetrical varieties with raised edges, that bear a strong resemblance to Operculinae.
368. Geographical and Geological Distribution.—The conditions under which this genus flourishes best are by no means the same as those which most favour the development of the two preceding types ; for some of the largest examples of Pulvinulina come to us from within the Arctic Circle, and plenty of good-sized specimens may be obtained from extreme depths. The examples which occur in the Algal zone, on the other hand, are for the most part the feeblest. It is, perhaps, on account of its prevalence at greater depths, that this type has been distinctly recognised at an earlier geological period than any other of the Rotalines; the P. elegans having been found so abundantly in the Upper Triassic clay of Chellaston by Messrs. Rupert Jones and Parker (lv), as to constitute nearly one-half of the Foraminifera in which that deposit is rich. The genus continues to present itself in the Liassic and Oolitic series, its examples being generally small but strongly limbate ; in the Gault their size increases, the limbation being still very strong ; and they become still larger in the Chalk-marl. It is very probable that these diversities have reference only to the depths at which the clay-beds that have been hitherto examined in these formations were respectively deposited. The highest development of this genus seems to have been in the Tertiary series, and especially in the Crag-formation.
Pulvinulina compiled by the pforams@mikrotax project team viewed: 21-9-2021
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