MESOZOIC AND CAINOZOIC DI NOFL AGELLATE CYSTS 201 



Remarks. In the form of the inner body, Netrelytron trinetron sp. nov. differs 

 from both other described species of the genus. It has only been recorded to date 

 from one horizon in the West Heslerton Bore, from which some six specimens have 

 been recorded. 



OTHER SPECTES 



Netrelytron jurassicum (Alberti 1961) from the Middle Jurassic (Bathonian-Callo- 

 vian) of Germany, is here transferred to this genus from Kalyptea on the basis of its 

 possession of an inner body within the spindle-shaped shell. 



Brosius (1963 : 38, pi. 3, fig. 2, pi. 4, fig. 2, pi. 5, fig. 4) has described a species 

 from the German Oligocene, as Netrelytron sp. nov. This corresponds in most 

 particulars to the emended diagnosis of Netrelytron, but lacks a cloak of debris. 

 Erection to separate generic status may prove appropriate. 



Genus PARANETRELYTRON nov. 



Derivation of name. Greek, para, near ; netron, spindle ; elytron, sheath, 

 husk — refers to the similarity of this genus to Netrelytron. 



Diagnosis. Cavate dinoflagellate cysts, enclosing body spheroidal to ovoidal 

 with apical horn ; inner body spheroidal. Shell lacking tabulation, with or without 

 traces of cingulum. Shell enclosed in cloak of adherent matter, formless to oval in 

 outline ; fragments of mineral matter and other sedimentary debris sometimes 

 embedded in cloak. Archaeopyle formation not known. 



Type species. Paranetr elytron strongylum sp. nov. Lower Cretaceous (Lower 

 Barremian) ; England. 



Remarks. This genus differs from Netrelytron in lack of an antapical horn and in 

 presence of indications of a cingulum ; and from all other described genera in the 

 possession of an outer cloak of organic debris. 



Paranetrelytron strongylum sp. nov. 

 PL 21, fig. 5 ; PI. 23, fig. 5 ; Text-fig. 52 



Derivation of name. Greek, strongylos, round, rounded. 



Diagnosis. A Paranetrelyton having a spheroidal outer body tapering smoothly 

 to form short, blunt apical horn. Inner body spheroidal and relatively large, 

 thin-walled and often hard to distinguish. A poorly-marked cingulum sometimes 

 present. Endophragm and periphragm smooth or only very minutely granular. 



Holotype. B.M.(N.LL) slide 51722(1). Speeton Clay, Shell West Heslerton 

 Borehole at 42-5 metres depth, West Heslerton, Yorks. Lower Cretaceous (Lower 

 Barremian). 



