466 BIDUULPHIA. 



IV. Eubiddulphie/E. Valves having at the apices pro- 

 cesses more or less obtuse, and of greater or less length. 



GENUS 132. BIDDULPHIA GRAY, 1831. 



Frustules free or united into filaments either continuous or in 

 zig-zag. Valves elliptic, suborbicular, triangular, quadrangular, etc. ; 

 margins even or undulated, usually more or less inflated at the median 

 portion, rarely depressed, showing elevated, obtuse processes at apices, 

 and having also sometimes hornlike processes. Girdle face more or 

 less quadrangular, showing distinctly processes which are not so 

 visible in the valve face. Connective zone very obvious. 



The genus Biddulphia is of vast proportions ; it includes some hundreds of 

 species and the genus requires a serious monograph written by a thoroughly 

 competent specialist who shall have devoted a very considerable time to its 

 examination and study. 



Many of the forms belonging to the genus Biddulphia have been 

 arranged in different genera. Genera have even been established, founded 

 simply on the number of angles of the valve, such are Triceratium, 

 Amphitetras, Amphipaitas, Polyceratium ; forms which are found at the same 

 time, and both rhomboidal and angular in form, for example, Biddulphia 

 rhombus (Ehr.) W. Sm., and its forma trigona Cleve {Triceratium slriolatum 

 Ehr.) show that these groups are not admissible. Although, according to the 

 general plan of this work, we are only concerned with the species inhabiting 

 the shores of the North Sea, I shall, nevertheless, give a figure of the type- 

 form of each Genus group which has been established by authors in the 

 genus Biddulphia as I understand it. These groups are as follows : 



Group. Biddulphia (fig. 197, Biddulphia pulchella Gray). 

 Odontella (fig. 198, B. {Triceratium) consimile Gr.). 



,, Odontella Lampriscus (fig. 199, B. [Triceratium) Shadboltianum Grev.). 



,, Zygoceros Ehr. (fig. 200, B. (Zygoceros) circinnus Bail.). 



,, Denticella Ehr. (fig. 201, B. (Denticella) granulata Roper). 



,, Cerataulus Ehr. (fig. 202, B. {Cerataulus) Smithii Ralfs). 



,, Pseudo-stictodiscus (fig. 203, B. {Pseudo-stict.) Eulensteinii Grun.) 



Triceratium (fig. 204, B. { Triceratium) Favus {Ehr.) H. V.H.). 

 ,, Amphitetras (fig. 205, B. {Amphitetras) antediluviana {Ehr.) H. V.H. ). 



,, Amphipentas (fig. 206, B. {Amphipentas) punctata Brightw. 



