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CONTRIBUTIONS FROM THE CUSHMAN LABORATORY FOR FORAMINIFERAL RESEARCH

VOLUME 23, PART 4

SHARON, MASSACHUSETTS, U. S. A.

December, 1947

No. 300.  A New Genus and some New Species of Foraminifera from the Upper Eocene of Ecuador

By J. A. Cushman and R. M. Stainforth

ROBULUS INSUETUS Cushman and Stainforth, n. sp. (Pl. 17, fig. 1)

Test close coiled, strongly umbonate, periphery acute with a narrow keel, somewhat lobulate; chambers distinct, not inflated, 9‑12 in number, increasing very gradually in size as added; sutures thick, with high ridges, very slightly curved, fusing at the center into an irregular umbonal boss; wall smooth except for the raised sutures; aperture peripheral, radiate. Diameter 0.75‑0.90 mm.; thickness 0.40‑0.45 mm.

Holotype (Cushman Coll. No. 54237) from the upper Eocene, Seca formation, sea cliffs at Punta Mambra, Ecuador.

This is a highly ornate species differing from R. alato‑limbatus (Gümbel) in the higher, more nearly radial sutures, distinctly lobulate keel, and smaller size. It is fairly common at the type locality and shows little variation in its essential characters.

PLECTOFRONDICULARIA DENTIFERA Cushman and Stainforth. n. sp. (Pl. 17, figs. 2, 3)

Test small, about twice as long as wide, very strongly compressed, periphery subacute and somewhat dentate; chambers distinct, not inflated, earlier ones of about half the test biserial, the last 2 or 3 in the adult uniserial, the periphery extending out into a short angular projection; sutures distinct, not depressed; wall smooth; aperture terminal, elliptical, occasionally with a very short neck. Length 0.45‑0.55 mm.; breadth 0.25‑0.28 mm.; thickness 0.04‑0.06 mm.

Holotype (Cushman Coll. No. 54239) from the upper Eocene, Seca formation, sea cliffs at Punta Mambra, Ecuador.

This species differs from P. packardi Cushman and Schenck, var. spinata Cushman and Schenck in the very much smaller size, very few uniserial chambers, and more compressed test, and from P. spinifera Cushman and Jarvis in the smaller size, larger proportion of biserial chambers, and the sutures not depressed.

BOLIVINOPSIS PULCHELLA Cushman and Stainforth, n. sp. (Pl. 17, figs. 4, 6)

Test elongate, strongly compressed, periphery acute but not keeled, center somewhat thickened, base broadly rounded, broad, sides slightly divergent; chambers numerous, the earlier ones close‑coiled forming about 1‑1/2 coils, then biserial throughout the adult stage, increasing very gradually in size as added with as many as ten pairs in the adult; sutures distinct, flush with the surface, strongly oblique; wall thin, finely perforate; aperture elongate, in the terminal face extending to the inner margin. Length 0.55‑0.80 mm.; breadth 0.22‑0.25 mm.; thickness 0.10‑0.12 mm.

Holotype (Cushman Coll. No. 54254) from the upper Eocene, San Mateo formation, subsurface core material from a well near Manta, Ecuador.

This species might be mistaken for a Bolivina if the early stages were missing. The close coiled portion has many chambers and is strongly raised in the center forming the thickest part of the test. The species differs from B. eocenica (Cushman and Barksdale) in the much more elongate form, higher and more numerous chambers, thin wall, and somewhat tapering test. The species is common at the type locality.

Genus BULIMINELLITA Cushman and Stainforth, n. gen.

Genoholotype: Buliminellita mirifica Cushman and Stainforth, n. sp.

Test elongate, spiral, with the spiral suture distinct; chambers usually three to five in each whorl; wall calcareous, perforate; aperture in the early stages elongate, loop‑shaped, in the adult terminal, rounded, with a distinct neck.—Eocene.

This genus is evidently derived directly from Buliminella with the adult developing a terminal aperture with a distinct neck.

BULIMINELLITA MIRIFICA Cushman and Stainforth, n. sp. (Pl. 17, figs. 6‑8)

Test small, irregularly fusiform, initial end subacute, greatest breadth slightly above the middle, circular in transverse section, apertural end tapering to a subacute point; chambers distinct, slightly inflated, three to five to a whorl, increasing very slightly in size as added; sutures distinct, slightly depressed, the spiral suture distinct and continuous; wall smooth; aperture in the early stage elongate, loop‑shaped, in the adult terminal, rounded, with a distinct neck. Length 0.35‑0.50 mm.; diameter 0.16‑0.20 mm.

Holotype (Cushman Coll. No. 54242) from the upper Eocene, Seca formation, sea cliffs at Punta Mambra, Ecuador.

This species is fairly common at the type locality and represents a development from Buliminella.

BULIMINA SECAENSIS Cushman and Stainforth, n. so. (Pl. 17, figs. 9, 10)

Test of medium size, tapering from the subacute to slightly rounded initial end to the greatest breadth above the middle thence decreasing in breadth to the rounded apertural end; chambers distinct, inflated, increasing rather rapidly but evenly in size as added, the basal portion somewhat contracted; sutures distinct, strongly depressed; wall with numerous longitudinal costae, mostly continuous across but some broken at the sutures; aperture nearly terminal, loop‑shaped, with the greatest width at the inner end thence tapering to a narrow opening at the basal margin of the chamber, with a slightly, developed rim. Length 0.50‑0.65 mm.; diameter 0.32‑0.38 mm.

Holotype (Cushman Coll. No. 54245) from the upper Eocene, Seca formation, sea cliffs at Punta Mambra, Ecuador.

This species differs from B. jacksonensis Cushman in the more inflated chambers and deeper sutures, giving an irregular outline to the test, and the less strongly developed sutures, some of which are not continuous from chamber to chamber.

BULIMINA LINEATA Cushman and Stainforth, n. sp. (Pl. 17, fig. 12)

Test rather small, slender, tapering from the slightly rounded or subacute initial end to the greatest breadth formed by the last one or two whorls, periphery only slightly lobulate, nearly circular in end view with a slight tendency to concavity at the sides; chambers distinct, only slightly inflated, numerous, increasing gradually and rather evenly in size as added; sutures distinct, slightly depressed; wall ornamented by fine longitudinal costae, continuous across the sutures, the last one or two whorls in the adult often smooth; aperture elongate, slightly oblique, in the terminal face of the last‑formed chamber extending from the inner margin a considerable distance into the terminal face. Length 0.50‑0.60 mm.; diameter 0.17‑0.22 mm.

Holotype (Cushman Coll. No. 54248) from the upper Eocene, San Mateo formation, subsurface core material from a well near Manta, Ecuador.

This species differs from B. semicostata Nuttall in the slenderer, more evenly tapering form, and fewer costae.

BULIMINA ACUTANGULARIS Cushman and Stainforth. n. sp. (Pl. 17, fig. 13)

Test small, initial end subacute, evenly tapering with the greatest breadth near the upper portion of the last whorl, apertural end obliquely truncate, irregularly triangular in transverse section, the earlier portion with acute angles; chambers rather indistinct, increasing rather rapidly in size as added; sutures rather indistinct, slightly depressed in the later portion; wall with very coarse longitudinal costae, somewhat irregular; aperture semi‑elliptical, fairly large, with the greatest breadth at the base of the last‑formed chamber. Length 0.37‑0.42 mm.; breadth 0.20‑0.23 mm.

Holotype (Cushman Coll. No. 54250) from the upper Eocene, San Mateo formation, subsurface core material from a well near Manta, Ecuador.

This species is common at the type locality. It differs from B. truncana Gümbel in the irregular costae, more concave sides, and more angled periphery.

BULIMINA DECURTATA Cushman and Stainforth, n. sp. (Pl. 17, fig. 11)

Test rather small, very short and broad, initial end subacute, greatest breadth near the middle, apertural end broadly rounded, the last whorl making up nearly the entire surface of the test; chambers few, increasing very rapidly in size as added, inflated; sutures distinct, slightly depressed; wall smooth; aperture loop‑shaped, extending from the inner margin of the last‑formed chamber well into the terminal face, curved, but of nearly uniform width, with a slightly thickened border. Length 0.45‑0.60 mm.; diameter 0.40‑0.50 mm.

Holotype (Cushman Coll. No. 54252) from the upper Eocene, San Mateo formation, subsurface core material from a well near Manta, Ecuador.

This species differs from B. guayabalensis Cole, var. ampla Cushman and Parker in the larger proportion of the surface occupied by the chambers of the last whorl, and the more tapering base.

EXPLANATION OF PLATE 17

Fig. 1. Robulus insuetus Cushman and Stainforth, n. sp. x 45. a, side view; b, peripheral view. 2, 3. Plectofrondicularia dentifera Cushman and Stainforth, n. sp. x 60. 2, Holotype. 3, Paratype. 4, 5. Bolivinopsis pulchella Cushman and Stainforth, n. sp. x 60. 4, Holotype. 5, Paratype. 6-8. Buliminellita mirifica Cushman and Stainforth, n. gen., n. sp. x 60. 6, Holotype. 7, 8, Paratypes. 9, 10. Bulimina secaensis Cushman and Stainforth, n. sp. x 45. 9, Paratype. 10, Holotype. 11. B. decurtata Cushman and Stainforth, n. sp. x 45. 12. B. lineata Cushman and Stainforth, n. sp. x 60. a, front view; b, apertural view. 13. B. acutangularis Cushman and Stainforth, n. sp. x 60. a, front view; b, apertural view.

14. Quinqueloculina naheolensis Cushman, n. sp. x 60. a, b, opposite sides; c, apertural view. 15. Q. plummerae Cushman and Todd, var. flectata Cushman, n. var. x 60. 16. Textularia portenta Cushman, n. sp. x 60. a, front view; b, apertural view. 17. Spiroplectammina paleocenica Cushman, n. sp. x 60. a, front view; b, apertural view. 18, 19. Textularia plummerae Lalicker, var. arkansasana Cushman, n. var. x 45. 18, Holotype. 19, Paratype.