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UNITED STATES NATIONAL MUSEUM BULLETIN 215 



but some resemble very closely the specimen figm-ed by 

 Cushman and Todd (1945a). Unfortunately the type 

 description does not give any detaU as to the variability 

 of the species. It is therefore not possible to decide 

 whether the Trinidad specimens can definitely be 

 included in ChUoguembelina mauriciana. 



The specimens here referred to ChUoguembelina cf. 

 mauriciana (Howe and Roberts) are shorter and thicker 

 than G. martini (Pijpers). The aperture is lower and 

 often more symmetrical in shape and position. Many 

 transitional forms exist, however, between the two 

 groups, but they are here separated as they have dif- 

 ferent stratigraphic ranges. 



Length: 0.14-0.22 mm. 



Occtjrkence: Navet formation (Eocene), Hantkenina 

 aragonensis zone to Porticulasphaera mexicana zone. 



Types: Figured hypotypes (USNM P5764, 5765a, b, 

 5766) and unfigured hypotypes (USNM P5767). 



Chiloguembelina midwayensis midwayensis (Cushman) 



Plate 21, Figure 1; Tbxt-figuke 14 (24^27) 



Giimbelina midwayensis Ctjshman, 1940, p. 65, pi. 11. fig. 15 

 (Paleocene, Alabama, U. S. A.) — Cushman and Todd, 

 1946a, p. 58, pi. 10, fig. 15 (Paleocene, Arkansas, U. S. A.). — 

 Cushman, 1951, p. 37, pi. 11, figs. 7, 8 (Paleocene, Alabama, 

 Arkansas, and Texas, U. S. A.). 



The greatest number of typical specimens occurs in 

 the Globorotalia fusilla pusilla zone. In the overlying 

 G. pseudomenardii zone the variability of the species 

 becomes greater, and at the same time closely related 

 forms appear, i. e., Chiloguembelina crinita (Glaessner) 

 and C. midwayensis strombiformis, new subspecies. 



A characteristic not mentioned by Cushman in his 

 original description is the asynometrical shape of the 

 aperttire, an important featiu^e of the Chiloguembelina 

 midwayensis group and other species of Chiloguembelina. 



Length: 0.2-0.3 mm. 



Occurrence: Lower Lizard Springs formation (Paleo- 



Types: Figured hypotypes (USNM P5768, P5769a-d) 

 and unfigured hypotypes (USNM P5770). 



Chiloguembelina midwayensis strombiformis Beckmann, new 



subspecies 



Plate 21, Figuke 6; Text-figure 14 (28-31) 



Test rapidly increasing in breadth, slightly com- 

 pressed laterally. Periphery roimded. Chambers 

 shghtly inflated, biserially arranged, with their aper- 

 tural faces not at right angles to the plane of greatest 

 breadth of the test, thus giving the test a twisted appeai- 

 ance. Sutures depressed, slanting. Wall finely spinose. 

 Apertm-e large, broader than high, surrounded by a 

 transparent collar. One side of the apertm-e projects 

 more than the other; its position is therefore oblique 

 with regard to the general shape of the test. 



Holotype from the Paleocene, lower Lizard Springs 

 formation, Globorotalia pseudomenardii zone; Trinidad 

 Petroleum Development Co. well Moruga No. 15, south 

 Trinidad (coordinates N: 149878 links, E: 497002 linlu), 

 core 3720^0 feet (TTOC 223472), 



The variability of Chiloguembelina midwayensis 

 strombijormis is illustrated by the text-figures 14, num- 

 bers 28-31. It increases more rapidly in size than 

 Chiloguembelina midwayensis midwayensis and has a 

 more spinose wall, more oblique sutures and a broader 

 aperture. It is separated from Chiloguembelina crinita 

 (Glaessner) by the lower, le>s globular chambers, the 

 slightly coarser spinosity of the wall and the broader 

 aperture. 



Length: 0.23-0.3 mm. ; holotype, 0.25 mm. 



Occurrence: Lower Lizard Springs formation (Pale- 

 ocene), Globorotalia pseudomenardii zone (common) and 

 Globorotalia velascoensis zone (rare) . 



Types: Figured holotype (USNM P5771) and para- 

 types (USNM P5772 a-d), unfigured paratypes 

 (USNMP5773). 



Chiloguembelina midwayensis subcylindrica Beckmann, 

 new I 



Plate 21, Figures 2, 3; Text-figure 14 (32-35) 



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. Cham- 

 bers biserially arranged, moderately inflated. Sutures 

 depressed, shghtly 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 aperttire is 

 sometimes covered by a small end chamber (pi. 21, 

 fig. 3). 



Holotype from the lower Eocene, upper Lizard 

 Springs formation, Globorotalia formosa formosa zone, 

 about 1^4 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 smaU Ampelu River tributary de- 

 scribed 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), coUected by K. W. Barr (No. 6972) (TTOC 

 102301). 



There is some variation in the length to breadth 

 ratio of the test aad 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 obhque sutures. The little 

 end chamber which covers the aperture of some speci- 

 mens of C. midwayensis subcylindrica is absent in other 

 subspecies of G. midwayensis. 



Length: 0.25-0.42 mm.; holotype, 0.4 mm. 



Occurrence: Upper Lizard Springs formation (lower 

 Eocene), Globorotalia rex and Globorotalia formosa 

 formosa zones. 



