20 DIATOMACE.E OF NORTH AMERICA. 



i Frustules traversely septate, or costate : cuneate, 



!>. angular, or sub angular 11 



' Frustules not as above 10 



( Frustules not much developed in f. v. (free), rarely 



angular, neither lunate nor cuneate 1M> 



j All others, filamentous, generally much developed 



in f. v ISC 



Valve disc more or less undulate, divided into regu- 

 lar compartments, usually alternate light and 

 1U. ! dark ; mostly with marginal or sub-marginal 



spines or teeth 18E 



Valves not as above 13 



r , \ Valves hyaline, with umbilical lines 1SF 



I Valves not as above 14 



i Valves with definite, irregular, flexuose, or bifurcate 



14.- rays; not hispid, nor with marginal spines 18F 



(. Valves not as above l. r > 



1r ( Valves hyaline, rays definite, not reaching margin... 1SF 



( Valves not as above 16 



( Valves with spathulate, cordate, or deltoid rays, their 



1(5. -N bases frequently forming a hyaline central area 18F 



(. Valves not as above 17 



t Valves with large marginal hyaline spaces, which 



17. are neither circular nor hexagonal isl<" 



( All others 18G 



(' A CHJETO(.'ERE;K 



B MELOSIRE.E (X.) 



! C BlDDULPHIE.E (XI.) 



is. ; D EUPODISCE.E (XII.) 



E HKI.IOPELTE^ (XIII.) 



F. ASTEROLAMPREJE. (XVI.) 



ANALYSIS OF THE GENERA. 

 Names of the Genera printed in Italics are not North American. 



TRIBE I. KAPHIDIE.E. 

 FAMILY* I. CYMIJELLE.K. 



f Frustules sometimes complex : frequently hyaline, 

 or inflated or constricted in f. v. : with central 

 nodules approximate, and touching the connecting 

 /me; median line often indexed. Valves fre- 

 quently with a transverse line istauros 1 ; "con- 

 necting membrane'' often longitudinally striate or 

 punctate AMI'IK>I;A i. 



, Frustules not as above 1 



