5 



Amphipleura Kuetz. — Valvae lanceolatae, convexae, utrinque carinatae, nodulo 

 centrali nullo v. subnullo, rhaphe recta, nodulis terminalibus hinc inde 

 distiuetissimis, elongatis; striae subtilissimae (Frustula fusiformia). 



** Valvse rhaphem arcuatam vel sigmoideam ostendentes. 



Okedenia Eul. — Est Amphipleura rhaphe subsigmoidea. 



Staurosigma Grun. — Characteres Stanroneidis sed rhaphe sigmatoidea. 



Pleurosigma W. Sm. — Valvae naviculaceae, plus minus sigmoidese, striis 



longitudinalibus, transversis et saapius simul obliquis ornatae, nodulo cen- 



trali rotuudato vel oblongo, rhaphe sigmatoidea. 

 Scoliopleura Grun. — Valvie naviculaceae, valde convexae, tortae spiraliter 



et tunc rhaphem et zonam connectivalem plus minus oblique sigmatoi- 



deas praebentes (incl. Alloioneis Schum. p. m. p.). 

 Rhoicosigma Grun. — Frustula achnanthiformia, rhaphe sigmatoidea (incl. 



Achnanthosigma Reinh.). 

 Toxonidea Donk. — Frustula leviter torta, e facie connectivali visa arcuata, 



zona connectivali diagonali-percursa, valvae lateribus non symmetricis, 



striatae, rhaphe arcuata. 

 Donkinia Pritch. — Frustula e facie connectivali visa medio constricta pan- 



duriformia, zona connectivali recta; valvse hneares, rhaphe sigmatoidea, 



abrupte excentrica, marginem attingente (Genus ad Amphiproraceas ver- 



gens). 



B) Frustula intra massam mucosam vel tubos mucosos, subinde figuratos 



nidulantia (Schizonemece auct.). 



* Sine stratu interiori costarum. 

 •J- Genera aquae dulcis. 



Colletonema (Breb.) V. H. — Valvae struetura paullo excentrica donatae, no- 

 dulis terminalibus ab apice valvarum remotis striisque radiantibus di- 

 scretis. Frustula tubis mucosis inclusa, 



Frustulia Ehr. — Valvao ut in Navicula, nodulis et centrali et terminalibus 

 inter duplicem rhaphem sitis. Frustula in tubis mucosis vel muco difformi 

 inclusa. [Ex Cleve in litt. idem ac Vanheurcfcia Bre"b.]. 



•f-f- Genera marina. 



Schizonema (Ag.) Grun. — Characteres Colletonematis sed tubulis mucosis 



flguratis algasque majores simulantibus. Frustula Naviculce! (incl. Phly- 



ctcenia Kuetz. p. p., Micromega Kuetz. etc). 

 Berkeleya (Grev.) Gruh. — Frustula in muco amorpho vel subgloboso vel in 



tubulis mucosis inclusa, fere amphipleuroidea; valvaa nodulum centralem 



deduplicatum (rhaphe interposita nulla) prsbentes. 

 Dickieia Berk. — Characteres Schizonematis sed massis mucosis foliaceis ul- 



vaeformibus. Frustula Stauroneidis ! 



C) Frustula stipite mucoso suffulta. 

 Brebissonia Grun. — Frustula Amphipleurce similia. 



