CATALOG OF ORIGINAL DESCRIPTIONS: Chiloguembelina midwayensis subcylindrica Beckmann 1957
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Citation: Chiloguembelina midwayensis subcylindrica Beckmann 1957Taxonomic rank: sub-speciesType specimens: Plate 21, Figures 2, 3; Text-figure 14 (32-35); Figured holotype (USNM P5774) and para- types (USNM P5775, 5776a-d), unfigured paratypes (USNM P5777).Type sample (& lithostrat): upper Lizard Springs formationType age (chronostrat): lower Eocene, Globorotalia formosa formosa zoneType locality: about 1¼ miles southeast of the junction between the Eio Claro-Guayaguayare Road and the road to the abandoned Lizard Springs oilfield, southeast Trinidad, 120 feet north of small Ampelu River tributary described as type section of the Lizard Springs formation by Cushman and Renz (1946), and 130 feet east of Ampelu River (coordinates N:187160 links, E:556600 links), collected by K. W. Barr (No. 6972) (TTOC 102301).Type repository: Washington; USNM
Original Description Test large for the genus, rapidly increasing in size in the early stages, only slightly increasing in the later portion, which may become almost cylindrical. Chambers biserially arranged, moderately inflated. Sutures depressed, slightly slanting. Wall very finely spinose. Aperture fairly large, about as broad as high, oblique to the plane of greatest breadth of the test, usually with a narrow transparent collar. The aperture is sometimes covered by a small end chamber (pl. 21, fig. 3). Size: Length: 0.25-0.42 mm.; holotype, 0.4 mm. Extra details from original publication Remarks: There is some variation in the length to breadth ratio of the test and in the degree of inflation of the chambers as shown in the text-figure. Chiloguembelina midwayensis subcylindrica, new subspecies, differs from G. midwayensis midwayensis (Cushman) in the larger size of the test, the greater increase in size of the early chambers, and in the shape of the later part of the test, which is much thicker and often almost cylindrical. It is separated from G. midwayensis strombiformis, new subspecies, by its larger size, more cylindrical test, higher chambers and less obique sutures. The little end chamber which covers the aperture of some specimens of C. midwayensis subcylindrica is absent in other subspecies of G. midwayensis.
Occurrence: Upper Lizard Springs formation (lower Eocene), Globorotalia rex and Globorotalia formosa formosa zones.
References:
Beckmann, J. P. (1957). Chiloguembelina Loeblich and Tappan and related foraminifera from the Lower Tertiay of Trinidad, B.W.I. 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: 83-95. gs
Chiloguembelina midwayensis subcylindrica compiled by the pforams@mikrotax project teamviewed: 17-8-2026
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Beckman1957 pl21-02.JPG
holotype illus_1147.jpg
Beckman1957 pl21-03.JPG
Beckman1957 pl21-02.JPG
holotype illus_1147.jpg
Beckman1957 pl21-03.JPG
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