'5S SYSTEMATIC HISTORY OF THE INFTJSOEIA. 



P [ Valres with pervious costre or striae Eunotie.e. 



'^' \ „ a longitudinal line or keel Surirelle^. 



P f Frustules cuneate in the front view 7 



I ,, not cuneate in the front view 11 



f. I Frustules free ; valves with aire Surirella. 



'■ I ,, attached or united in filaments ; valves without alse ,. . 8 



c j Valves dotted, dots not forming striae Eucampia. 



„ not dotted, or the dots arranged in transverse lines 9 



' Frustides radiating from a common centre ; valves obovate or 



clavate 10 



,. not radiant ; valves with symmetrical ends Fragilarie^. 



' Frustules in front ^dew \^dth longitudinal vittiB Licmophorej:. 



„ ,, without longituduiai vittse (costse per- 

 vious) MERTDIE.E. 



" Connecting zone (annvdate) with imperfect internal septa Striatelle.e. 



,, „ without internal septa 12 



{ Lateral view witli 3, or more, angles or lobes Angulifer^e. 



12. s „ ,; circular 17 



[ ,, ,, neither angular nor circular 13 



(Valves not conspicuous in front view, which is mostly longer 

 than broad 14 



„ compressed, inflated, conspicuous in front view, which is 

 mostly broader than long 15 



^ , J Valves with a longitudinal line Surirelle.e, 



[ ,, without a longitudinal Hne Fragilarie.e. 



-J ^ r Valves in front view, rectangular, with transverse capitate vittre . Terpsinoee. 



^•^^ I „ „ with produced angles, processes, or spines 16 



1 f, J Valves cellulose, symmetrical Biddulphie.e. 



I „ not cellulose, mostly dissimilai* Ch.etocerke. 



{Frustules saddle-shaped ; valves mostly with longitudinal blank 

 space Campylodiscus. 

 „ not saddle-shaped ; central blank space (if any) orbicular 18 



-.Q ( Valves cellulose 19 



°' { „ not cellulose Melosire.e. 



{Frustules simple ; lateral view more conspicuous than front 20 



„ either imited into filaments or front view broader than 

 lateral Melosire.e. 



90 i Valves fmiiished with projecting processes Eupodisce,e. 



I „ without processes, but sometimes vrith minute teeth Coscinodisce.e. 



B. 



rt, f Only one valve with a central nodule 22 



\ Botii valves with central nodules 23 



i^,^ r Frustules adnate, not genuflexed Coccoxeide.e. 



"*" i „ not adnate (often stipitate), genuflexed Achnanthe^. 



(Frustules cuneate in front view ; valves usually with dissimilar 

 ends GoMPHONEME^. 

 ,, not cuneate; valves with symmetrical ends 24 



o - r Median line rib-like and distinct ; nodides distinct 25 



I ,, not rib-Kke ; nodides mostly obscure 2 > 



Side view kmate ; nodide mostly excentric 26 



,, not lunate (rarely lunately curved) ; nodule central ... Navicule.e. 



op r Valves venti'icose, stride not decussating Cymbelle-b. 



I ,, not ventricose, striae decussating Toxonidea. 



C. 



Individuals of one piece, with radiating spines Actinisce.e. 



Families. 

 * Valves without a central nodule. 

 Eunotiea?. Meridieae. Licmophoreag. Fragilarieoe. Synedi'ea?. Smdrellea^. Stria- 

 tellese. Terpsinoese. Biddulphieae. Angulifereae. Eupodisceae. Coscinodisceae. Melosirese. 

 Chaetocerca\ 



2* Vah'CH. unth a median line and a central nodule. 



C"occov.ddca\ Admanthoa\ Cymbelleae. Gomphonemeae. Naviculese. 



Actinisceae, 



