CALCAREOUS ALGAE OF THE MIDDLE EAST 31 



of the living Acetabularia. The latter character was described by Morellet, but not 

 well figured, on Algerian material. 



The pioneer study on Middle East (Qatar) material was by F. R. S. Henson in an 

 unpublished report of 1942. He distinguished a minority of C. jurassica conforming 

 strictly with the type-description, and more numerous examples with a higher 

 sporangial-tubule count. In a preliminary examination of Middle East algae 

 (Elliott 1955b) I recorded these latter as C. cf. hanabatensis Yabe & Toyama, com- 

 paring them with this Japanese species which has a higher count (22-24, U P to 27), 

 but is a larger species (verticil-diameter up to 3-5-4-0 mm.). This determination 

 is now abandoned. 



Detailed comparative statistical studies of local populations of Clypeina jurassica 

 from different circum-Mediterranean and Middle East countries have not been made 

 to my knowledge. Such studies would have to be made on good collections of 

 complete, isolated, verticils, since the recognition of proportional, as opposed to 

 structural, differences, in random thin-section material is a task of great difficulty, 

 at any rate with the small degree of difference expected in the present problem. The 

 results would have to be interpreted in the light both of presumed salinity changes, 

 from facies and accompanying fauna, a factor affecting living algae, and also bearing 

 in mind possible post-mortem sorting of verticils of slightly differing size and shape 

 from mixed assemblages of dissociated component-verticils derived from associated 

 plants. It seems likely that the local differences revealed, at any rate in the main 

 Tethyan basin, would depend on these secondary factors rather than on a progressive 

 evolutionary trend. 



C. jurassica is a frequent and characteristic fossil for much of the Upper Jurassic 

 of the western old-world Tethys ; in the east, it is missing from rocks of this age in 

 Borneo. The oldest level appears to be in Algeria (Rauracian-Sequanian of Morellet 

 1951, equalling Upper Oxfordian of current usage) ; the species occurs throughout 

 the Mediterranean Kimmeridgian and is especially abundant at levels of Portlandian 

 or Tithonian age over the whole of its distribution-area. In my experience it extends 

 to the very top of the Upper Jurassic and is a good index-fossil for the upper part of 

 the Upper Jurassic. (See also comments below (p. 87) on the Jurassic-Cretaceous 

 boundary.) 



In the Franco-Swiss area, from which the types were described, there are records 

 from the lowest Cretaceous (infra- Valanginian and Berriasian, e.g. Donze 1958a, b). 

 This is in an area adjacent to a region of uplift with terminal Jurassic — early Creta- 

 ceous freshwater brackish and lagoonal beds of Purbeck type : the algae are con- 

 sistently smaller than those from the Jurassic. They may be a transitional form to 

 the succeeding C. inopinata (rare or absent in the Middle East), their evolution a 

 reaction to salinity-changes. Donze suggested, that they were either a different 

 species, close to C. inopinata, or stunted C. jurassica " bad adaption to environ- 

 ment ". The relation of these and other algae to salinity is discussed below under 

 environment. In Jugoslavia Kercmar (1962) has described a local variety C. 

 jurassica minor, which he distinguishes from the typical C. jurassica jurassica mostly 

 by the smaller size, there being little if any overlap or transition in this character. 



