Desmid. p. 227.; Ealfs, in Annals, vol. xv. pi. xi.
fig. 5.; Jenner, in loc. cit. p. 194.
Ilab. Eustliall Common, near Tunbridge Wells; and
Rackham .Common, near Pulborough, Sussex: ilf?--
Jenner. Dolgelly : ilfr. R a fs .
The angles in this species are not as in the others prolonged
into rays, and this will at once serve to distinguish it from
those species.
2. S t a u r a s t r u m ? t e t r a c e r u m R a fs .
Plate L X X X IV . Fig. 4.
Char. Frond rough. Segments but slightlg constiicted, qua-
drform. Outer angles prolonged into diverging rays
ivhich are entire at their extremities. E nd view compressed,
with a process at each extremity.
S ta u r a s trum p a ra d o x um Ehr., Infus. p. 143. t. 10. fig. 14.
A lic r a s te r ia s tric e ra and te tra c e ra Kfitz., Synops. Desmid.
in Linnaja, 1833, p. 602. figs. 83, 84, 85.; Ralfs, in
Annals, vol. xv. pi. x. fig. 1.
Hab. Dolgelly and Penzance: Mr. Ralfs.
The minute granules with which the frond is covered form
transverse lines on the rays, and give them a jointed appearance.
This species, in its compressed ellipsoidal form in the
end view, would appear to approach closely the genus A r-
throdesmus.
3. S t a u r a s t r u m p a r a d o x u m Meyen.
Plate L X X X V . Fig. 3.
Char. Fronds rough, constricted. Ends truncate. F ro n t view
elongated, diverging processes minutely trifid. E nd view
usually quadrangular, but sometimes triangular.
Meyen, Nov. Act. Scap. Holm. vol. xiv. p. 43. figs. 37. 38.;
ISIenegh. Synops. Desmid. p. 227. Micrasterias Staurastrum
Kiitz., in Linnaia, p. 399.; Ealfs, in Annals
vol. X V . p. 151. pi. X . fig. 2.
Ilab. Dolgelly and Penzance: Mr. Ralfs.
This Staurastrum is to be distinguished from the previous
species hy the trifid extremities of the rays.
4. S t a u r a s t r u m ? b i e id u m Rolfs.
Plate L X X X V . Fig. 2.
Char. Frond smooth, but little constricted in the centre, truncate
laterally. Rays trifid. End view triradiate.
Desmidium hifidum Ehr., Die Infus. p. 141. t. 10. f. 11.;
Ralfs, 1. c. p. 151. pi. X . fig. 3.
Hah. Dolgelly and Penzance: Mr. Ralfs.
The smoothness of the frond will always distinguish this
from the previous species. It should probably be referred to
Trigonocystis.
Section iii. P e n t a s t e r i a s Ehr.
Char. Frond in front view without diverging processes. End
view circular, with usually fiv e rags.
Derivation. From r r £ V T S , f i v e , and a a - T s p i a s , starred.
1. P e n t a s t e r i a s a r a c h n i s Hass.
Plate L X X X V . Fig. 8.
Char. Frond rough, deeply constricted in the centre. Segments
about as long as broad, suborbicular, with elongated
slender hyaline and incurved processes. End view five-
rayed.
Staurastrum Arachne Ralfs, in Annals, vol. xv. p. 157.
pi. xi. fig. 6.
Hab. Boggy pool near Dolgelly, very rare: Mr. Ralfs.
“ This plant is remarkable for its slender processes which
will easily distinguish it from St. margaritaceum. It cannot
be a five-rayed variety of St. gracile, for the rays are longer,
more slender, remarkably incurved, and also entire at the
extremity.” — Ralfs.
A A 2