MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 173 



OTHER SPECIES 



The following species are here included in the genus Prolixosphaeridium nov., on 

 the basis of shape, character of processes and possession of an apical archaeopyle : 



Prolixosphaeridium mixtispinosum (Klement i960). Upper Jurassic ; Germany. 



Prolixosphaeridium parvispinum (Deflandre 1937a). Upper Cretaceous ; France. 



The following species, inadequately described and figured, is doubtfully referred 

 to this genus : 



IProlixosphaeridium xanthiopyxides (O. Wetzel 1933). Upper Cretaceous ; 

 Germany. 



OTHER MESOZOIC AND CAINOZOIC SPECIES ATTRIBUTED TO BALTISPHAERIDIUM 



In the preceding section, the bulk of post-Palaeozoic species, hitherto placed in 

 Baltisphaeridium, have been reattributed to four new genera on the bases of shape, 

 process arrangement and possession of archaeopyles. The species Baltisphaeridium 

 spinosum (White) is considered in the previous chapter ; it is shown to be probably 

 synonymous with Hystrichodinium pulchrum Deflandre but since the holotype of B. 

 spinosum is lost, restudy is not possible. The abandonment of the name spinosum is 

 therefore proposed. The species Baltisphaeridium geometricum (Pastiels) was 

 originally placed in the genus Hystrichosphaeridium and was then a junior homonym 

 of a species proposed by Deflandre (1945) ; since invalid at the time of publication, 

 this name must be rejected. Pastiel's forms are attributable to the genus Wetzeliella 

 and are discussed more fully on p. 192. 



The holotypes of the two species, Baltisphaeridium ferox (Deflandre) and B. tri- 

 dactylites (Valensi) were re-examined recently by one of the authors (R.J.D.) in 

 consultation with Prof. Deflandre. On the basis of this re-examination, their 

 reattribution to Hystrichokolpoma is here proposed. Reattribution of two species, 

 (Baltisphaeridium neptuni Eisenack 1958 and B. triangulatum Gerlach 1961) to the 

 genus Achomosphaera is proposed on pp. 51, 52 ; and in the discussion of the genus 

 Hystrichosphaeridium and its allies (see pp. 53-105) the reattribution of two further 

 species to new genera is proposed, Baltisphaeridium dictyophorum (Cookson & 

 Eisenack) becoming Oligosphaeridium and B. striatoconus (Deflandre & Cookson) 

 becoming Litosphaeridium. 



Five further species currently attributed to the genus Baltisphaeridium appear also 

 to merit reattribution. Four species from the German Tertiary, three of them attri- 

 buted by Maier (1959) to her invalid genus Galea and subsequently reattributed by 

 Downie & Sarjeant (1963) to Baltisphaeridium (B. galea ; B. lychneum ; B. rehdense ; 

 and B. twistringense) are herewith tentatively reattributed to the genus Areoligera on 

 the basis of archaeopyle structure. The species Baltisphaeridium placacanthum (De- 

 flandre & Cookson) is herewith reattributed to Systematophora, since the processes 

 show the grouping characteristic of the latter genus. 



A residue of Mesosoic and Tertiary species remain, which either appear definitely 

 acritarchs or whose morphology is not at present sufficiently well known for any 



