76 CALCAREOUS ALGAE OF THE MIDDLE EAST 



arranged at regularly-spaced levels, the pores alternating in position from level to 

 level, and Radoicic, who figured them as dasyclad verticils of lateral branches, 

 indicated (op. cit., fig. i) that the distance between adjacent external pores of one 

 verticil was twice the distance between successive verticils. In Radoicic's type- 

 figures, e.g. pi. 4, fig. 1, this regularity is very clearly shown, and other writers, e.g. 

 Reiss 1961 (figs. 101, 105, etc.) also show this. In the types of Hensonella (Elliott 

 i960, pi. 8, fig. 1) this regularity is absent, and I drew attention to the irregularity. 

 Reiss (op. cit. : 229), commenting on this, adds that the pores " occur in all suitably 

 sectioned specimens ", meaning presumably sections taken at pore-level, and such 

 specimens have been seen not uncommonly in slides of Middle East Hensonella. 



The thick yellowish layer was described for Hensonella (Elliott i960 p. 229) as 

 aragonite. This was incorrect : it is calcite, and both Dr. A. Lees (Reading Univer- 

 sity) and Mr. J. McGinty (Iraq Petroleum) consider it derived from an original 

 organic calcite structure. 



Crushed examples from Algeria show the thick layer broken along radial partings, 

 but in most cases still held together by the inner thin dark layer. If the crushing 

 occurred during compaction, this suggests original organic nature for the thin layer, 

 with some flexibility. Edgell (in lit., i960), who also supported the dasyclad nature 

 of the organism, suggested that this layer may be the original algal wall, or thickened 

 organic outer layer of the stem-cell, and this appears to be the view of Radoicic also 

 (op. cit. : 38). That it was an original part of the organism is indicated both by its 

 almost invariable presence irrespective of all but the very worst preservation, and by 

 occasional specimens in which it is lined by a secondary inner layer of post-mortem 

 calcite, possibly pre-burial, the actual tube-core within this being clear, transparent 

 calcite deposited after burial from solution. The large canals which expend to the 

 exterior are sometimes seen in random cut to reach this dark inner layer, and, 

 following Reiss's reasoning on their external appearance, may similarly be supposed 

 normally to do so when the sections are suitably orientated. 



Summarizing, S. dinarica Radoicic and Hensonella Elliott were described from 

 examples of the same organism, and the great majority of subsequent records refer 

 to this same species. Slight differences in the two author's descriptions can be 

 reconciled by examination of large sets of specimens. Since the fossil agrees in size, 

 shape, and morphological structure with other dasyclads, and also occurs in suitable 

 facies at suitable levels for this, Radoicic described it as a dasyclad, referring it to 

 Salpingoporella and comparing it carefully with S. miihlbergii of the same age. A 

 similar comparison is possible with the new S. arabica. This dasyclad reference 

 seems to be the majority view of other workers, as expressed in synonymy or by 

 comment. 



In spite of this, there remain certain doubtful features which seem incompatible 

 with a dasyclad origin. In living dasyclads, the deposition of the original aragonitic 

 calcium carbonate is connected with the " assimilatory processes in the chlorophyll 

 corpuscles " (Church 1895), and the calcified layers or structures built up of fine 

 granules are amorphous. By contrast, the calcium carbonate of marine inverte- 

 brates (molluscs, brachiopods, corals, echinoderms, etc.) is deposited out of solution 



