. Bulletin of the British Museum (Natural History), Geology. 31* MID-TERTIARY CYTHERETTINAE DISCUSSION OF THE SUPERSPECIES C. TEN U IP U N CTATA The stratigraphically arranged series of specimens from the Paris Basin shows certain trends. The earhest species, C. minipundata sp. nov. and C. huttensis sp. nov. huttensis subsp. nov., have very weakly developed ridges with several rows of puncta between them. In the later species the ridges become stronger and the puncta in between them become larger with fewer rows, as in C. tenuipundata absoluta and C. tenuipundata lirata. In the latter the ridg
. Bulletin of the British Museum (Natural History), Geology. 31* MID-TERTIARY CYTHERETTINAE DISCUSSION OF THE SUPERSPECIES C. TEN U IP U N CTATA The stratigraphically arranged series of specimens from the Paris Basin shows certain trends. The earhest species, C. minipundata sp. nov. and C. huttensis sp. nov. huttensis subsp. nov., have very weakly developed ridges with several rows of puncta between them. In the later species the ridges become stronger and the puncta in between them become larger with fewer rows, as in C. tenuipundata absoluta and C. tenuipundata lirata. In the latter the ridges are very strong and the pitting is reduced to a single row of large pits. It is considered that the relationships suggested in Fig. 23 represent a possible phylogeny. The barrier may be ecological rather than geographical sensu strido. C. minipunc- tata, or something like it, is a possible ancestor of C. tenuistriata with its two recorded geographical sub-species. It is interesting to note that in Switzerland the finely punctate species with weak ridges, C. variabilis and C. bernesis, occur at a stratigraphically lower horizon than C. tenuistriata tenuistriata, as in the Paris Basin. In the Mainz Basin these postu- lated early forms are not present, possibly because the Sannoisian is poorly exposed, but more likely because they were not present in the area; they have not been found in samples collected nor recorded in the works of Triebel, Stchepinsky and Gramann. In the Chattian of the Mainz Basin there are, however, two finely punctate forms, C. ramosa ramosa (Lienenklaus) and C. ramosa sublaevis (Triebel). The valve of the former has an uneven surface, similar to C. variabilis, and both of these are only tentatively included in the superspecies. C. ramosa sublaevis has a much smoother valve with fine punctae between weak ridges. C. stigmosa Triebel has a similar ridge pattern, but varies in shape and has much larger pitting. The two must be closely related, however. The L
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