CORAL STUDY IN THE SOUTHERN OCEAN — SQUIRES 457 



Unfortunately, it is here that the Southern Ocean fails to provide 

 us with the required data, for as yet the Antarctic Continent has re- 

 fused to yield information on the distribution of Tertiary Corals. To 

 date the oldest records of corals are from raised morame deposits in 

 the McMurdo Sound area of the Koss Sea and these have been dated as 

 Pliocene. The coral identified from these deposits is Gardlneria 

 antarctica and it is a member of the modern fauna. However, there 

 are two other areas which have close relationships to the Antarctic : 

 South America and New Zealand. Although the f amia of the former 

 has been studied only in a most general way, it apparently is of re- 

 stricted age range and of restricted environmental types. The Tertiary 

 fauna of New Zealand has, on the other hand, been demonstrated to 

 be extremely rich and to represent a wide span of ages and of environ- 

 mental types. 



Perhaps one of the most interesting aspects of a study of the New 

 Zealand Tertiary Mollusca by C. A. Fleming was the apparent move- 

 ment through time of the position of the Subtropical Convergence 

 deduced from the distribution of these fossils. This movement, later 

 also fomid to be demonstrated by the distribution of corals is recorded 

 in the fossil record by the progressive migration, first south, and then 

 north of the cold-water faunas of New Zealand. For example, during 

 the Miocene, coral reefs existed in the northern portion of the North 

 Island, indicating that the Subtropical Convergence was farther to 

 the south than at present, for water temperatures in the vicinity of 

 North Cape are now only just about warm enough to support the most 

 hardy of the reef corals. However, after a brief episode, these coral 

 reefs were exterminated by cooling marine climates and the warm- 

 water fauna which had penetrated far to the south was slowly driven 

 northward. Finally, all New Zealand was occupied by a cool-water 

 fauna during the Pleistocene. Now there is apparently a reversal and 

 new immigrants from the northern, warmer waters are appearing. 

 It may well be that in some time not too long in the future, the northern 

 portions of New Zealand may again be ringed by protective coral reefs. 



From this type of study, we can expect a picture of the present-day 

 distribution of corals and hypotheses of their past distribution to 

 emerge. From these results much can be deduced regarding the mecha- 

 nism by which the corals (and other faunal elements) have migrated, 

 and of the controls upon their distribution. Because many elements 

 of the study of larval life are as yet beyond experimental means, re- 

 quiring pressure and temperature controls which make them prohibi- 

 tive, deductions based upon distributional information regarding larval 

 life will be the sole means for gathering this type of data for some 

 time to come. Much information regarding the geological history of 

 the Antarctic region can be derived from additional faunal inf orma- 



