32 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



authors (R.J.D.). The preparations, which are now in the Humboldt University, 

 Berlin, were kindly lent for examination by Dr. K. Diebel whose assistance is 

 gratefully acknowledged. 



Specimens of X. furcatum as illustrated by Ehrenberg (1838, pi. 1, figs. 12, 14) 

 cannot be traced and are either not distinctive enough for sure identification with 

 his drawings or they have subsequently been lost. It is therefore proposed to treat 

 the complex as one species to be designated Hystrichosphaera ramosa, since none of 

 the specimens of X. furcatum as figured by Ehrenberg has been positively identified 

 by later workers. The specimen figured by Ehrenberg (1838, pi. 1, fig. 15) is erected 

 as the holotype of H. ramosa and the species is regarded here as the type species of 

 the genus. Since Ehrenberg did not designate a holotype or give a description of 

 H. furcata, and since later workers have failed to recognize it, it is proposed that 

 forms attributed to H. furcata since 1933 be transferred to H. ramosa Ehrenberg. 



Hystrichosphaera ramosa, in its revised acceptation, is an extremely long ranging 

 species exhibiting a very considerable degree of variation in the detail of its mor- 

 phology. Many of the extreme variants, encountered in isolation, would be con- 

 sidered sufficiently morphologically distinct from the typical forms to justify their 

 erection as separate species ; but consideration of the whole assemblage shows all 

 intermediate stages to be represented. However, our present knowledge of the 

 species suggests that particular variational trends may have occurred only at certain 

 stages within the total range of the species ; the extreme variants are capable of 

 ready recognition and may prove of value as stratigraphical indices. A number of 

 varieties are therefore here proposed, distinguished on the bases of process number 

 and form, combined with character of the periphragm. Each represents the extreme 

 development of a particular structure or combination of structures ; intermediate 

 stages to the typical H. ramosa var. ramosa are in all cases known and are even 

 frequent, so that differentiation of these forms at a higher taxonomic level is con- 

 sidered inappropriate. 



Hystrichosphaera ramosa (Ehrenberg) 



Emended diagnosis. A species of Hystrichosphaera possessing a thin walled 

 central body, smooth, reticulate or granular. Gonal + sutural processes always 

 extending beyond confines of sutural crests, solid or hollow, the latter closed distally. 

 Typical gonal processes trifurcate, sutural processes bifurcate, both commonly 

 terminating distally in a small bifurcation. 



Holotype. Slide "Feuerstein von Delitzsch, no. XXV" of Ehrenberg, Institut 

 fur Palaontologie und Museum der Humboldt Universitat, Berlin. Upper Creta- 

 ceous ; Germany. 



Stratigraphical range. This species has been recorded as H. furcata from the 

 Oxfordian by Deflandre (1938) and Sarjeant (i960). Pleistocene examples have 

 been observed by a number of workers, e.g. Fries (1951) and Rossignol (1964), and it 

 has also been recorded from post-Pleistocene sediments dated 950 B.C. from West 

 Wales. (Churchill & Sarjeant, in progress.) 



