STUDIES IN FORAMINIFERA 



57 



Globotruncana concavata (Brotzen) 

 Plate 13, Figures 3a-c 



Rotalia concavata Brotzen, Zeitschr. Deutsch. Ver. Palaestinas, 



vol. 57, p. 66, pi. 3, fig. b, 1934. 

 Globorolalia asymetrica Sigal, 19th Congr. G^ol. Internat., 



Monogr. Il€g., ser. 1, No. 26, p. 35, fig. 35, 1952. 

 Globotruncana (Globotruncana) ventricosa ventricosa White, 



Dalbiez, Micropaleontology, vol. 1, No. 2, p. 168, figs. 



7a-d, 1955. 



Shape of test: very low trochospiral, spiral side often 

 slightly concave, umbilical side strongly convex; equa- 

 torial periphery distinctly lobate with closely spaced 

 double keel. Wall: calcareous, perforate, surface 

 smooth. Chambers: hemispherical; 15-20, arranged in 

 3-3 K whorls; the 5-6 chambers of the last whorl increase 

 rapidly in size, early whorls small by comparison. Su- 

 tures: spiral side distinctly curved, depressed; imibUical 

 side radial, depressed. Umbihcus' deep, wide. Aper- 

 tures: primary apertures interiomarginal, umbilical; 

 tegiUa with accessory apertures not preserved in 

 examined specimens. Coiling: predominantly dextral; 

 of 50 specimens counted, only 3 coUed sinistrally. 



Dimensions of figured hypotype: diameter 0.69 mm.; 

 thickness 0.4 mm. 



Range: Globotruncana concavata zone, Naparima 

 Hill formation. 



Type and occurrence: Figured hypotype (USNM 

 P4798) from Trinidad Leaseholds well Marac 1, Trini- 

 dad (coordinates N:152141 links, E:424447 links), 

 sample from core 8,180-8,237 feet (TLL 175917). 



Remarks: The characteristic features of Globotrun- 

 cana concavata (Brotzen) are similar to those of Globo- 

 truncana ventricosa White. Through the courtesy of 

 Dr. B. F. EUis, some specimens of Globotruncana ven- 

 tricosa from White's original collection at Columbia 

 University, N. Y., were obtained for comparison with 

 specimens of Globotruncana concavata from Israel 

 (original locality), Tunisia, and Trinidad. It was 

 found that the two species differ as foUows: 



Globotruncana ventricosa as a rule has 6-7 chambers 

 in the last whorl with slightly more oblique sutures on 

 the spiral side, as against usually 5 chambers with 

 slightly curved sutures in Globotruncana concavata. 

 The spiral side of Globotruncana concavata is often 

 slightly concave, that of Globotruncana ventricosa is flat 

 or slightly raised. Compared with Globotruncana 

 concavata, the 2 peripheral keels in Globotruncana 

 ventricosa are a little further apart and more strongly 

 developed, and the sutures are often beaded. Finally, 

 the stratigraphic range of the two species is different: 

 Globotruncana concavata appears to be restricted to the 

 upper part of the Coniacian and the Lower Santonian, 

 Globotruncana ventricosa to the Upper Santonian and 

 the Campanian. Because of their similarity, the two 

 species may easily be mistaken. The specimen figured 

 by Dalbiez (1955) as Globotruncana ventricosa ventricosa 

 is, in the author's opinion, a Globotruncana concavata. 

 Globotruncana ventricosa carinafa Dalbiez is probably 

 identical to Globotruncana ventricosa White, while 



Globotruncana ventricosa primitiva Dalbiez could be 

 close to Globotruncana renzi Gandolfi, judging from the 

 single peripheral view given by Dalbiez and the strati- 

 graphic range quoted by him. According to Dalbiez's 

 range chart, the three species {Globotruncana ventricosa 

 primitiva {=G. Irenzi), G. ventricosa ventricosa {=G. 

 concavata) and G. ventricosa carinata (=?(j. ventricosa 

 White) follow each other in time. Transitional speci- 

 mens suggest that they probably represent an evolu- 

 tionary sequence. 



Globotruncana ventricosa White 

 Plate 13, Figures 4a-c 



Globotruncana canaliculata var. ventricosa White, Journ. Pa- 

 leontol. vol. 2, No. 4, p. 284, pi. 38, figs. 5a-c, 1928. 



Shape of test: very low trochospiral, nearly flat or 

 slightly convex on spiral side, strongly convex on the 

 umbQical side; equatorial periphery lobate, with 

 distinct, robust double keel, often weakened in last 

 chambers. Wall: calcareous, perforate, surface smooth. 

 Chambers: angular, inflated; 15-20, arranged in 2^-3 

 whorls; the 6-7 chambers of the last whorl increase 

 moderately in size. Sutures: spiral side: curved, 

 strongly raised, beaded in early portion; mnbilical side: 

 slightly curved, depressed. UmbUicus: deep, wide. 

 Apertures: primary apertures interiomarginal, um- 

 bilical; tegilla with accessory apertures not preserved 

 in examined specimens. Coiling: the limited number 

 of specimens seen coiled dextrally. 



Dimensions of figured hypotype: diameter 0.63 mm.; 

 thiclcness 0.34 mm. 



Range: Globotruncana stuarti zone, Naparima Hill 

 formation. 



Type and occurrence: Figured hypotype (USNM 

 P4799) from Usine Ste. Madeleine Quarry, southeast 

 end of Naparima Hill, San Fernando, Trinidad (coor- 

 dinates N:235800 links, E:364000 links), sample Bt. 37 

 (TLL 151935). 



Remarks: See remarks under the description of 

 Globotruncana concavata (Brotzen). 



Globotruncana inornata Bolli, new species 

 Plate 13, Figures 5a-6c 



Shape of test: low trochospiral, biconvex; equatorial 

 periphery strongly lobate, early chambers of last whorl 

 rounded at periphery, last and occasionally penultimate 

 chambers compressed with sharp peripheral edge or 

 faint keel. Wall: calcareous, perforate, surface of 

 early chambers in well preserved specimens showing 

 some rugosity. Chambers: subangular, compressed; 

 14-16, arranged in 3 whorls; the 4 chambers of the last 

 whorl increase rapidly in size, early whorls small by 

 comparison. Sutures: spiral side slightly curved, de- 

 pressed ; umbilical side: straight, depressed. Umbilicus: 

 shallow, wide. Apertures: primary apertures interio- 

 marginal, umbilical; tegilla with accessory apertures 

 poorly preserved in examined specimens. Coiling: 

 predominantly dextral; of 50 specimens counted, only 

 4 coiled sinistrally. 



