MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 61 



Hystrichosphaeridium arborispinum sp. nov. 

 PI. 9, figs. 5, 10 



Derivation of name. Latin, arbor, tree ; spinus, spine — with reference to the 

 tree-like appearance of the processes. 



Diagnosis. Sub-spherical to ovoidal central body composed of thin endophragm 

 and granular or reticulate periphragm. Processes, composed of periphragm, 

 hollow, tubiform, usually simple, expanding distally and terminating with complica- 

 ted secate margin. Apical archaeopyle commonly present. 



Holotype. B.M.(N.H.) slide ¥.51727(3). Speeton Clay, Shell West Heslerton 

 Borehole No. 1, Yorkshire at 39 metres depth. Lower Cretaceous (Middle Barremian). 



Dimensions. Holotype : diameter of central body 39 by 39fx, length of processes 

 io-i9(x. Range : diameter of central body 31-43^, length of processes 10-23^. 

 Number of specimens measured, 4. 



Description. The distal extremities of the processes have a distinctive ragged 

 appearance due to the irregular shape of the secae — some being irregularly lobate, 

 others giving off spines laterally. Specimens with fibrous processes, and more 

 rarely with fenestrate processes, have been observed. An apical archaeopyle 

 commonly seems to be present, but its precise nature is difficult to determine for 

 the specimens are extremely thin walled and easily distorted. The number of 

 processes seems to be standardized at 22 to 23, and this together with their arrange- 

 ment on the surface of the central body indicate that H. arborispinum sp. nov. has a 

 reflected tabulation similar to that of H. tubiferum. 



This species has been recorded only from the Lower and Middle Barremian of 

 Yorkshire. 



Remarks. The form of the distal extremities of the processes characterizes this 

 species and distinguishes it from all other described species. 



H. arborispinum is basically of the same type as H. tubiferum (Lejeune-Carpentier 

 1940) but has slightly broader processes which are distally much more divided. 



Hystrichosphaeridium salpingophorum (Deflandre) 

 PI. 10, fig. 6 



1935. Hystrichosphaera salpingophora Deflandre : 232, pi. 9, fig. 1. 



1937. Hystrichosphaeridium salpingophorum (Deflandre) Deflandre : 80, pi. 13, figs. 1, 3. 



1940. Hystrichosphaeridium salpingophorum (Deflandre) ; Lejeune-Carpentier: 219, text-fig. 8. 



1947. Hystrichosphaeridium salpingophorum (Deflandre) ; Deflandre, text-fig. 1, no. 7. 



?i948. Hystrichosphaeridium salpingophorum (Deflandre) ; Pastiels : 37, pi. 3, figs. 3-7. 



?i952. Hystrichosphaeridium salpingophorum (Deflandre) ; W. Wetzel : 399, text-fig. 11. 



?I952. Hystrichosphaeridium salpingophorum (Deflandre) ; Gocht, pi. 1, fig. 19 ; pi. 2, fig. 20. 



1952. Hystrichosphaeridium salpingophorum (Deflandre) ; Deflandre, text-fig. 11. 



1955. Hystrichosphaeridium salpingophorum (Deflandre) ; Deflandre & Cookson : 271, pi. 2, 



fig- 9- 

 ?i958. Hystrichosphaeridium salpingophorum (Deflandre) ; Eisenack : 401, pi. 27, figs. 5, 6. 



