274 DISCOVERY REPORTS 



ambiguity have become inapplicable. When dealing with a genus, which, owing to 

 inadequate description, contains a host of alien forms, it is reasonable to suggest that as 

 the genus must stand or fall by the type species, certain characters of, or facts pertaining 

 to, the type species should be used to establish more clearly the generic limits. To define 

 the limits of the genus Biddulphia as interpreted by Van Heurck, would be a matter of 

 great difficulty, or to be able to say definitely what is or what is not a Biddulphia would 

 be an impossibility. 



The type of the genus, Biddulphia pulchella Gray, exhibits admirably the characters 

 of the genus as I would interpret it. The cells are elongated about the pervalvar axis. 

 The valves are oval to oval-lanceolate in outline, occasionally constricted. The angles 

 of the valves are produced to short but stout processes, slightly capitate. The valve 

 surface is covered with coarse puncta arranged in irregular concentric lines in the central 

 area. The central area is often furnished with two short, blunt spines, but these may be 

 much reduced or absent. The valve mantle is often deep, sparsely punctate. The girdle 

 simple, punctate. The cells frequently unite to form chains, often joined so that the 

 valves are face to face, but they may be joined by one angle only, giving a zigzag 

 appearance to the chain. 



Upon such characters I define Biddulphia. Much variation is found amongst the 

 species. The number of angles present may be two, three, four or more, but mostly two 

 or three. The processes in the angles vary in shape and size, they may be small and 

 rounded, or flattened so as to appear as an area merely marked off from the rest of the 

 valve surface by a sulcus ; or they may be large, erect and inflated, usually terminated by 

 an area of either fine or coarse pores. The valve surface is punctate. The puncta may be 

 exceedingly fine, granulate or spiny, but never hexagonally areolate. Isolated spines, 

 usually large, may or may not be present upon the central area of the valve, and they are 

 often developed more strongly upon the outer valve of a terminal member of a chain. 

 The valves are often traversed by sulci which separate the angles from the central area, 

 and the margins of the valves are frequently strengthened by costae or canaliculi. In 

 habit the genus is mainly colonial and truly planktonic, neritic or oceanic, confined 

 chiefly to temperate and subtemperate waters. The oceanic species often show great 

 diversity in form and structure, particularly with regard to the degree of silicification. 

 Generally speaking, holoplanktonic species are less strongly siliceous than meroplank- 

 tonic ones. 



Biddulphia antediluviana (Ehrenberg) Van Heurck. 



Van Heurck, 1885, p. 207, pi. 109, figs. 4, 5. 

 Amphitetras antediluviana Ehrenberg, 1840 a. 

 Triceratium antediluvianum (Ehrenberg) Grunow, 1870, p. 24. 



Cells angular, solitary, strong. Valves possessing four angles. Valves gently concave 

 along the margins, valve centre depressed. Valve surface covered with large coarse 

 areolation. Areoles subrectangular, arranged in concentric lines in the central area, 

 irregularly parallel, subradiate, or sometimes slightly curved in the angular portions of 



