SYSTEMATIC ACCOUNT 277 



Biddulphia polymorpha (Grunow) Wolle. 



Wolle, 1890, pi. 97, figs. 5, 11. 

 Hustedt, 1930, p. 851, fig. 505. 

 Cerataulus polymorphs Grunow ex Van Heurck, 1881, pi. 104, fig. 3. 



Cells somewhat rectangular in girdle view, broadly oval in valve view. Valve surface 

 flat or weakly convex. The poles of the valves are furnished with short but wide, almost 

 circular processes. Valve surface covered with puncta. Puncta irregularly arranged in 

 the central area of the valve, but in curved lines proceeding to the processes, in the polar 

 axis between them. The puncta are arranged in straight lines radiating from the centre 

 in the lateral areas of the valve. The whole surface of the valve is covered with short 

 spinulae arranged in irregularly radiating lines. A group of larger spinulae, usually six 

 in number, form an irregular ring around the central area. Girdle finely striate, striae 

 moniliform. Chromatophores : numerous rounded bodies. Polar axis 120-140/x ; trans- 

 apical axis 80-120/*; pervalvar axis, 120/*. 



Observed at St. WS481. 



Biddulphia anthropomorpha Van Heurck. (PL XIII, fig. 5.) 



Van Heurck, 1909, p. 39, pi. 10, figs. 136-7. 



Biddulphia punctata Greville, var. Van Heurck, 1909, p. 41. 



Biddulphia OttomuUeri Van Heurck, 1909, p. 40. 



Biddulphia OttomuUeri, var. rotunda Van Heurck, 1909, p. 41. 



Biddulphia punctata, var. subtriundulata Van Heurck, 1909, p. 41. 



Biddulphia punctata, var. subaurita Van Heurck, 1909. 



Biddulphia translucida Van Heurck, 1909, p. 42. 



Biddulphia litigiosa Van Heurck, 1909, p. 40. 



Biddulphia polymorpha Mangin, 1915, p. 27. 



Cells gonioid, usually united to form chains. Valves bipolar, broadly oval to elliptic- 

 lanceolate. Angles furnished with stout processes, terminally inflated. In some speci- 

 mens the processes are ill-defined, and have the appearance of flattened areas, separated 

 only from the central area by a sulcus in the valve surface. The central area of the valve 

 is slightly inflated and frequently bears two stout spines, which diverge slightly. Valve 

 surface covered with punctation, puncta spinous. Spines strongly developed on some 

 cells, weakly on others, while on very young cells the spines may be absent altogether. 

 Beneath the process the valve is slightly constricted, but evenly so. Valve mantle deep. 

 Girdle usually simple, but may exhibit a few annular lines, sometimes finely striate, but 

 often hyaline. Chromatophores : numerous rounded bodies. Polar axis 30-80/x ; per- 

 valvar axis 60-130/u. 



Mangin (191 5) became convinced that all the species and varieties created by Van 

 Heurck in 1909 were but growth forms of one genotype, and explained that the degree 

 of silicification, length of process, form of punctation and the presence or absence of 

 spines could not be regarded as characters of specific value. He found frequently that 

 the cells in the middle of a chain would possess some of the characters of one species, 

 while the terminal cells possessed characters of another, and was able to trace specific 

 continuity through the whole group. Mangin collected all the forms referred to under 



