CRYPT0-RAPHID1E/E. 



411 



TABLE OF TRIBES. 



Frustules cylindrical or flattened. Valves alike, terminated by a calyptra 

 (hood), pointed with a bristle ; or frustules with valves unlike or mostly 

 smooth ; furnished with awns, horns (elongated processes), spines or seta;, 

 which in fossil forms are sometimes imperfect or absent ; frustules often 

 imperfectly silicious. Valves without radial or cellulose costae ; or again, 

 frustules imperfectly silicious, united in distant series; connecting zone 

 more or less turgid. Valves angular, with a long central spine . 



I Frustules cohering ; girdle face generally much developed and cylin- 

 drical ; firmly silicious. Valves rarely hyaline ; unlike or elliptic and 

 without median line, sometimes apiculate or conical or with a peculiar 

 central nodule (spine); or umbilicus, smooth, punctate or cellulate, 

 and frequently with marginal or submarginal spines. Frustules 

 cohering either by teeth or marginal spines, or by a central spine 

 or a short central cushion ..... 



Girdle face much developed, valves of very different forms, some- 

 times furnished with horns or simple spines or prominences at 

 the apices ; always without ocelli or radiating septa . 



D 

 > 

 Z 



Chsetocerese. 



Melosirese. 



Biddulphiese. 



<L> 



o 



2 1 



O 



c 



as 

 > 



Valves round 



or elliptic, | Compartments alternately elevated and depressed Heliopeltese. 



divided into j 



radiating ] 



compart- | Compartments arranged on the same plane . Aster Olamprese 



merits. (. 



Valves not 

 divided into 

 radiating 

 compart- 

 ments. 



f Valves always round or very broadly elliptic, 

 furnished with one or more ocelli or with very 

 short obtuse horns, simulating ocelli . Eupodisceae. 



Valves generally round or elliptic, rarely elonga- 

 ted, semi-lunar or cuneate ; with cellulate or 

 punctate structure ; sometimes furnished with 

 small, short and slender spines, always without 

 ocelli ..... Coscinodiscus. 



