170 



•UNITED STATES NATIONAL MUSEtTM: BULLETIN 216 



expedition core 25E-1 (19°40' N., 168°32' W.) de- 

 scribed by Hamilton (1953) is almost identical with 

 that of the Hantkenina aragonensis zone or the basal 

 part of the Globigerapsis kugleri zone of the Navet 

 formation. Many of the specimens which are other- 

 wise indistinguishable from those described here as 

 Olohorotalia bullbrooki BoUi, new species, show distinct 

 supplementary suttiral apertures on the spiral side, a 

 feature that could not be seen in the Trinidad speci- 

 mens due to poor preservation. It seems most likely 

 therefore, that Glohorotalia bullbrooki from the Navet 

 formation should be placed in the genus Truncorota- 



The fauna of dredge sample 33C (17°45' N., 174° 

 16' W.), described by Hamilton as Paleocene, is com- 

 parable with that of the Globorotalia velascoensis zone 

 of the Lizard Springs formation of Trinidad (BoUi, 

 1957a). Another possibihty is that it represents a 

 horizon between the Paleocene Globorotalia velascoensis 

 zone and the lower Eocene Globoratalia rex zone of the 

 Lizard Springs formation, where a stratigraphic break 

 is indicated in the Trinidad section. Together with 

 Globorotalia velascoensis (Cushman), numerous Trun- 

 corotaloides types were found in the well preserved 

 material. The study of the dredge sample would 

 suggest that there are Truncorotaloides types identical 

 with or very close to species described under the names 

 Globorotalia wilcoxensis Cushman and Ponton, G. 

 iormosa gracilis Bolli, and G. aeqva Cushman and Renz. 



The fact, that Truncorotaloides appears in the 

 Paleocene makes it likely that some lower Eocene 

 species, so far attributed to the genus Globorotalia, 

 might also possess supplementary sutural apertures 

 on the spiral side which have not been observed because 

 of poor preservation. One such species likely to 

 belong to Truncorotaloides is Globorotalia quetra BoUi. 



All known Truncorotaloides species belong to the 

 group of distinctly spinose forms which appeared in 

 the upper Paleocene and apparently became extinct 

 at the end of the nodddle Eocene. 



Truncorotaloides rohri Bronnunann and Bermudez 



Plate 39, Figures 8-12c 



Truncorotaloides rohri Bronnimann and Bermtjdez, Journ. 

 Paleontol., vol. 27, No. 6, pp. 818-819, pi. 87, figs. 7-9, 

 1953. — Beckmann, Eclog. Geol. Helvetiae, vol. 46, No. 2, 

 p. 396, pi. 26, figs. 10, 11, 1953. — Bolli, Loeblich, and 

 Tappan, U. S. Nat. Mus. BuU. 215, p. 42, pi. 10, figs. 

 5a-c, 1957. 



Steatigkaphic range: IHantkenina aragonensis 

 zone; Globigerapsis kugleri zone to Truncorotaloides 

 rohri zone, Navet formation. 



Locality: Figured hypotypes (USNM P5751a-e) 

 from the Porticulasphaera mexicana zone, Navet 

 formation: same locality as given for Hastigerina micra 

 (Cole) (p. 161); sample Hg 8581 (TTOC 215782). 



Eemarks: In addition to Truncorotaloides rohri, 

 Bronnimann and Bermudez (1953) described three 

 varieties of this species which illustrate the variation 

 of chamber and test shape ranging from rounded to 

 angular forms. In T. rohri var. guara^araensis are 

 included specimens with spherical chambers. T. rohri 

 var. piparoensis is an intermediate form between T. 

 rohri var. guaracaraen^is and T. rohri. The chambers of 

 T. rohri var. mayoensis are angular conical, the test 

 umbilicoconvex. This variety may be regarded as 

 related to T. topilensis (Cushman). 



Truncorotaloides topilensis (Cushman) 



Plate 39, Figures 13-16b 



Globigerina topilensis Cushman, Contr. Cushman Lab. Foram. 

 Res., vol. 1, No. 3, p. 7, pi. 1, figs. 9a-c, 1925. 



Steatigraphic range: Globigerapsis kugleri zone to 

 Porticulasphaera mexicuna zone, Navet formation. 



Locality: Figured hypotypes (USNM P5752 a-d) 

 from the Porticulasphaera mexicana zone, Navet forma- 

 tion; same locality as given for Hastigerina micra (Cole), 

 (p. 161); sample Hg 8581 (TTOC 215782). 



Remarks: The Trinidad specimens of Truncorota- 

 loides topilensis (Cushman) compare closely with the 

 holotype of Globigerina topilensis Cushman, except 

 that many specimens possess sutural, supplementary 

 apertures on the spiral side, such as characterize the 

 genus Truncorotaloides. 



References 



Bandt, O. L. 



1949. Eocene and Oligocene Foraminifera from Little Stave Creek, Clarke County, Alabama. Bull. 

 Amer. Paleontol., vol. 32, No. 131, pp. 1-210, pis. 1-27. 

 Beckmann, J. P. 



1953. Die Foraminiferen der Oceanic Formation (Eocaen-Oligocaen) von Barbados, Kl. Antillen. 



Eclog. Geol. Helvetiae, vol. 46, No. 2, pp. 301-412, pis. 16-30, 29 text-figs. 

 1957. Chiloguembelina Loeblich and Tappan and related Foraminifera from the lower Tertiary of 

 Trinidad, B. W. I. U. S. Nat. Mus. BuU. 215, pp. 83-95, pi. 21. 

 Bermudez, P. J. 



1949. Tertiary smaller Foraminifera of the Dominican Republic. Cushman Lab. Foram. Res.i 

 Spec. Publ. 25, pp. 1-322, pis. 1-26. 



