<'ONSI>K<Trs OF THE KAMI I. IKS AM) <;K\KK'\. L>1 



{ Frustules simple, arcuate in s. v.. linear in f. v.. 



raphe and central nodule marginal in s. \ . . valve 



1. ! sonietimes inflated in the center of ventral margin 



( 'KI.'ATOXKIS II. 



All others, raphe frequently curved ('YMISKKKA in. 



FAMILY II. NAVMTLK.K. 

 c Frustules compound, valves with loenli (marginal 



cells) MASTOGLOIA iv. 



(. Frustules not as above 1 



Frustules compound (each valve with two plates >: 

 one (superior) with transverse ribs, the other 



1. -| (inferior) striate, with raphe and nodules 



STUTODKS.MIS v. 



I Frustules not as above 2 



c Valves with a conspicuous, transverse, smooth sili- 



2. - cious band istauros' not a late STAUKOXKIS vi. 



( V al ves not as above :> 



{ Valves sigmoid, or arcuate ; or frustules alate, or 



3. s raphe inflexed or renexed ."> 



I Valves and frustules not as above 4 



t Valves with a central nodule NAVKTKA vn. 



4. - Valves without central nodule (or obscure).. 



( AMPHIPLEURA vin. 

 f Valves symmetrically divided by the raphe : frus- 

 tules not alate, rarely constricted in f. v 



PLEUKOSKJMA ix. 



Valves or frustules not as above <> 



Valves not symmetrically divided by the raphe, 

 which is arcuate, ends renexed, and marginal.. 



0. ! TOXOMDIA X. 



All others, alate, usually constricted in f. v 



AMPHIPROHA xi. 



FAMILY III. GOMPHOXE.ME^:. 



i Frustules curved in f. v., nodule on concave valve... 



EHOIKOSIMIKMA xn. 

 (. All others O< >M riK IXKM A xm. 



FAMILY IV. ACII.XAXTIII:.];. 



Free or stipitate ..Aciix \.\TIIKS \i\. 



FAMILY V. COCCONIDEJE. 



( Valves with marginal cells Ortlion<>ix \\ . 



i Valves not as above ' 



