28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



Vertical subspecies could not be identified without knowing the age 

 of the assemblage. 



There are, in the fossil record, several additional forms that can 

 be linked to the trilobus-sacculifer gradational series, such as G. 

 altiapertura and G. immatura. These forms have been treated in 

 different ways by various authors, but the treatment thus far has been 

 dominantly typological. As a result, the range of forms in G. trilobus 

 sensu lato is reasonably well known, but there is still a poor under- 

 standing of the nature of population structures at the various strati- 

 graphic levels. Parker (1962, p. 219) pointed out the necessity of 

 treating assemblages as populations, and it could be added that this 

 particular problem lends itself to a quantitative analysis, since the 

 distinctions between the subspecies involve gradational characters. In 

 order to determine the actual changes that have occurred in G. trilobus 

 sensu lato since the Miocene, it will be necessary to analyze statistically 

 the character of many assemblages from widely separated localities 

 ranging from Miocene to Recent; a formidable task, but only in this 

 way can a complete and realistic alignment of subspecies be attained. 



Thus, any present arrangement of subspecies must be considered 

 tentative and incomplete. It seems unnecessarily pretentious to force 

 subspecies into horizontal or vertical strait jackets, and it is much more 

 compatible with the evidence at hand to recognize subspecies as 

 dynamic populations in which the range of variation fluctuates through 

 time and space. 



Distribution. — Although Globigerinoides trilobus trilobus was not 

 as common, overall, as G. ruber, the ratio between the two species 

 varied considerably from station to station, and at a few stations G. 

 trilobus trilobus was the dominant species of Globigerinoides. Its 

 highest frequency was 45 percent, which was recorded in the fall at 

 station 8, in the Sargasso Sea. 



GLOBIGERINOIDES CONGLOBATUS (Brady) 

 Plate 8, figures 2, 3 



Globigerina conglobata Brady, 1884, Rep. Voy. Challenger, Zoo!., vol. 9, p. 603, 



pi. 80, figs. 1-5, pi. 82, fig. 5. 

 Globigerinoides conglobata Bradshaw, 1959, Contr. Cushman Found. Foram. 



Res., vol. 10, pt. 2, p. 40, pi. 7, figs. 5, 6.— B6, 1959, Micropaleontol., vol. 5, 



No. 1, pi. 2, figs. 7-12. 

 Globigerinoides sp. Bradshaw, 1959, Contr. Cushman Found. Foram. Res., 



vol. 10, pt. 2, pi. 7, figs. 16, 17. 



Throughout most of the test the coiling is trochospiral, but in the 

 last whorl the final 2 chambers overlap the umbilicus. In many 



