Catalog - Globigerina aequilateralis

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Globigerina aequilateralis

Citation: Globigerina aequilateralis Brady 1879

Type specimens: [Brady, 1884, Rept. Voy. Challenger, Zool., vol. 9, pl. 8o, figs. 18-21, X so]: Figs. 18-19, bottom specimens: 18a, 19a, lateral aspect; 18b, 19b, peripheral aspect; 20, surface specimen; 21, section of the shell.

Type locality: Not given. [Specimen illustrated in fig. 19 from "Challenger" Sta. 224, lat. 7°45' N., long. 144°20' E., in the North Pacific Ocean, in 1850 fathoms; fide Nuttall, 1927, Ann. Mag. Nat. Hist., ser. 9, vol. 19, p. 233.]

Type repository: Depository not given. [Specimen illustrated in fig. 19 deposited in the collections of the Zoological Department, British Museum (Natural History), London, Reg. no. 85.10.5.485; other figured specimens (figs. 18, 20-21) not found in any collection; fide Nuttall, loc. cit.]

"This is a variety approaching; Hastigerina in general form. The test is planospiral and symmetrical, not rotalian; it consists of but little more than a single convolution, and the whole of the segments are sometimes visible on both sides. The final segment is often smaller than the penultimate, as is sometimes also the case with Globigerina cretacea d'Orbigny."

[Brady, 1884, op. cit., p. 605]: "Test planospiral, compressed, bilaterally symmetrical, tvpically evolute; consisting of rather more than a single loosely-coiled convolution; segments usually about six in number, and all visible from either side of the shell, nearlv globular in shape, the last sometimes smaller than the penultimate; aperture an arched opening on the umbilical face of each segment. Diameter, 1/30 inch (0.84 mm.), more or less.

Diameter, 1/30 inch (0.84 mm.), more or less.

"Globigerina aequilateralis is the type of the planospiral as distinct from the rotaliform varieties of the genus. It approaches Hastigerina in general contour, but the arrangement of the chambers is usually if not invariably evolute instead of involute, and the shell-wall is relatively much thicker than in the latter genus. The test is somewhat finely porous, the perforations measuring about 1/6000 to 1/5000 inch (0.0042 to 0.005 mm.) in diameter. So far as has been observed, the surface specimens do not manifest to the same extent as those of many other species the tendency to assume a spinous condition.

"Globigerina aequilateralis occurs amongst the surface-microzoa from the North Atlantic and the North and South Pacific. It has also been found in the South Atlantic but only in bottom-dredgings. Its area of distribution appears to extend from off the southwest corner of Ireland, lat. 50° N., to the Cape of Good Hope, about lat. 35° S.

"There can be little doubt that one of the specimens figured by Egger (1857, Neues Jahrb. Min., etc., p. 296, pl. 11, fig. 4) under the name Cassidulina globulosa Egger belongs to the present species, so that its geological history dates back at least as far as the Miocene period. Ehrenberg gives a drawing of a very similar form, possibly the same (Phanerostomum asperum Ehrenberg, 1854, Mikrogeologie, pl. 30, fig. 26a-b) from the Chalk of the Island of Rugen."

References:

Bolli, H. M., Loeblich, A. R. & Tappan, H. (1957). Planktonic foraminiferal families Hantkeninidae, Orbulinidae, Globorotaliidae and Globotruncanidae. In, Loeblich, A. R. , Jr., Tappan, H., Beckmann, J. P., Bolli, H. M., Montanaro Gallitelli, E. & Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin . 215: 3-50. gs V O

Brady, H. B. (1879). Notes on some of the reticularian Rhizopoda of the "Challenger" expedition. I.- On new or little known arenaceous types. Quarterly Journal of Microscopical Science. 19: 20-63. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina aequilateralis Brady 1879

Globigerina aequilateralis

References:

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