95 

 I. INTRODUCTION. 



The present paper, containing an account of the Turbinolid 

 corals of the Cape, has entailed the careful examination of up- 

 wards of 2,000 specimens from the present collection, and in the 

 British Museum I investigated also over 1,000 specimens of the 

 genus Flabellum, the account of which it did not seem advis- 

 able to defer until the whole family should have been finishea 

 (see " Marine Investigations in South Africa" Vol. II., pp. 1 17- 

 154, 1902). In addition, it was necessary to carefully study the 

 genera not represented in the collection, a work which clearly 

 showed Duncan's classification* to rest on no scientific basis. 

 However, I have provisionally adopted that arrangement of 

 genera, preferring to leave the revision until I shall have worked 

 through all the different families. 



I would like here to express my indebtedness to the Govern- 

 ment Biologist of Cape Colony for entrusting me with the ex- 

 amination of the collection. All the specimens of the different 

 corals that came up in the dredge appear to have been taken and 

 carefully preserved. Their species may seem to be few, but 

 the large numbers of several have allowed a p;oper 

 examination to be made of their variabihty. The latter 

 is shown to be very great in solitary corals. It may be divided 

 into three classes:- — (i) that due to environment, (2) continuous, 

 and (3) discontinuous, or in other words, (i) vegetative, (2) nor- 

 mal, and (3) specific. The presence of all three is quite clear 

 m Heterocyathus aequicostatus, as it was also in Flabellum 

 riibrum,% (i) the general characteristics and sizes from different 

 depths and locahties ; (2) to some extent the variation within the 

 types, but in particular the meristic variations ; and (3) the exist- 

 ence of definite types. Indeed, the collection has enabled us 

 to get an insight into the variability of corals, such as must be 

 carefully considered in any future systematic work on the 

 Madreporaria. 



The anatomy of the polyps has also been studied, and as 

 far as it goes, confirms the diagnosis of the species from their 



* Jour. Linn. Soc, XVIII., pp. 1-204 (1^84). 



§ Vide also " Variatimi in V. rubrum," Proc. PJiil. Soc, Ciinih., Vo]. 

 XL, pp. 463-71- 



