COSCINODISCE^. 



59 



Tribe XXV. Coscinodisce/E. 



TABLE OF GENERA. 



A. Valves disciform, oval or elliptic. 



^ o f Valve with cellular structure 



1-3 



-CT3 J. 





Structure not 

 cellular. 



-I 



f Valves punctate, with scattered puncta, and furnished 

 with sinuous-reticulated lines 



I, Valves quite hyaline, furnished with stiff erect spines 

 ' Valves furnished with a projecting irregular ridge 



( >? . f Valves with puncta arranged in radiating rows, interrupted 

 by hyaline spaces ; centre often bulbous or with thinly scat- 

 tered puncta, no marginal spines, margin hyaline 



3 



-5 



o 



4-* 



.S 





H.<" J 



3^1 Valve delicate, small ; centre hyaline, granular, and with a 



u 



T3 



bfl 



o 



u 



a, 



o 



>> 





o 



o 



2 



^ circlet of marginal teeth 



r 



5; -j 

 a Jc 



is 



o m 

 c o 

 2j= 



Valve having a conspicuous pseudo-opening at the 

 centre . . . 



' Valves cellular, with a broad margin, with 

 structure different from that of the centre, 

 from which it is separated by a well-defined 

 margin, without spines 



bfl 

 'S 



c 

 o 



Pyxidicula. 



Liradiscus. 



Xanthiopyxis. 



Acantiiodiscus. 



Cosmiodiscus. 



Stephanodiscus. 

 Porodiscus. 



Craspedodiscus. 



r 



bo 



( ' in 



> 

 O 



> 



n 



t/5 u 



"2 . 

 rt"3 



.- a, 





Valve having a row of large 

 cells entirely marginal . Heterodictyon. 



Large oblong cells arrang- 

 ed in (estoon . 



Brunia. 



nS 

 > 



> 





5 



Large cells forming a ring, which 

 separates the centre from the 

 broad marginal btrder ; centre 

 cells arranged in curved or 

 spiral lines . 



Valve very finely punctate, showing on 

 two sides, about a third from the mar- 

 gins, an arc of pseudo-cells. The two 

 arcs united to one another by a row 

 ^ of spines .... 



( Valve having a marginal or submarginal pseudo- 

 nodule ; puncta in radiating rows of unequal length, 

 leaving usually subulate blank spaces 



Brightwellia 



Janischia. 



Actinocyclus. 



o 



-a 



Valves dissimilar, the superior with rows of 

 puncta in distant lines, alternately long and 

 short ; inferior valve with puncta in approxi- 

 mate rows of equal length . . Anisodiscus. 



: -a 

 : o 

 c 



' Valve disciform, punctate or cellular, without 

 any costse, septa or processes whatsoever, 

 except sometimes some very small teeth 



c3 

 > 



Coscinodiscus. 



Valves furnished with long horns, more or less 

 robust .... Gossleriella. 



