192 
tura Reinsch u. Xanthidiastrura paradoxura stellt Verf. als 
Synonyraa unter Onychonfìraa Ira ve Nordst. auf. 
Verf. theilt unterstehende Gattungen auf folgende Weise ein. 
Ciflind7'OC(/stis : A. Cyclocy stis. Sides not concave. B. Clitocy- 
stis. Sides concave. 
Closterium : A. Selenoceras Strongly incurved, lunate. B. 
Carapyloceras. Slighthy curved, lower raargin nearly straight 
C. Orthoceras. Frond n arre w, more or less bacilliforra. D . Stau- 
roceras Kiitz. 
Sph'otcenia : A. Monotrania. Endochrorae a single spirai band. 
B. Polytrania. Endochrorae in several spirai bands. 
Triploceras : A. Myrraechidiura. Fronds with rugose or no- 
dose sides; section stellate, or crenato-rotund. B. Bacteridiura. 
Fronds with plain or sraooth sides; section circular. 
Bocidium: I. Lateribus fere rectis, v. leniter curvatis. A. Orthi- 
dium. Celi. Iravibus, punctatis v. granulatis. B. Rutidiura. Celi, 
plus rainus rugosis. — II. Later. undulatis v. nodiferis. C. Ha rama- 
ti di ura. Celi, nodibus instructis; sectio stellatis D. Oedemati* 
dium. Celi, tumores ferentes; sectio circulares. — IH. Later. valde 
curvatis. E. Oontidium. Semic. plus rainus ovatis. 
Bysphinchium : A. Cylindrosphinctium , Form cylindrical. B. 
S phrarosph ine tiu m. Forra subglobose. 
Cosmarium: Sect. I. Frond ovai or circular, more or less, in 
generai outline. A. Cyclidìum. Semic. hemispherical. B. Nep h ri- 
dia m. Semic. ovai, elliptic, or reniform. C. Pyramidium. Semic. 
pyramidal. — Sect. II. Frond biglobate. D. Sphraridium. Semic. 
nearly or quite globular. — Sect. III. Frond angular, or angularly 
rounded. E. Tetridium. Semic. more or less quadrate. F. Gonati- 
dium. Semic. 6-or poly-angular. G. Tei ni dium. Angles produced 
at either thè apex or base of thè semic. 
Euastrum: Sect. I. Euastrum. Lob. poi. (v. apex) incisus. Sub- 
sect. a) Lateral raargins not, or indistinctly, lobate. Subgenus A. 
Cosraariastrum. Sinuate or incised at margins; frond circular or 
ovai. B. Colpodastrum. Sides sinuous; frond oblong, quadrate or 
pyramidal. — Sub-sect. b). Lateral margins distinctiy lobate. C. Am- 
blyastrum. Lobes normally obtuse, not radiately arranged. D. A c t i- 
nastrum. Lobes sub radiate. — Sect. IL Eucosmiura Nrag. Lob. 
poi. (v. apex) integer, non incisuram singulam ferens. 
Micrasterias : A. Holoeystis (Hass.) emend., lobis polar. indi- 
visisj lob, lat. transverse positis. B. Atomoeystis lobis poi. vix 
