1“
4. T r i g o n o c y s t i s h e x a c e r o s Hass.
Plate L X X X IV . F ig. 11.
Char. Fronds rough. Segments about twice as long as
broad, separated from each other hg a deep notch, twisted.
End view triangular, with concave sides and blunt entire
angles.
S. tricorne Meneghini, Synopsis Desmid. p. 225. Rinatella
tricornis Breb., Alg. Fal. p. 57. (1835). Desmidium
hexaceros Ehr., Abhand. der Akademie d. Wissensch.
zu Berlin (1832), ¡1.292.; Ehr. Die Infus. p. 141. t. x.
fig. 10. Staurastrum tricorne Ralfs, in Annals, vol. v.
p. 155. pi. xi. fig. 2. ; Jenner, in loc. cit. p. 194.
Hab. Shallow pools, Piltdown Common; Ashdown Forest;
Rusthall Common; between Mayfield and Hadlow
Down: A ir. Jenner. Barmouth: Rev. T. Salweg. Dolgelly
and Penzance : Mr. Ralfs. High Beech: A. H. H.
“ The conic granules arranged in transverse lines at the
angles are generally very minute, but in some Sussex specimens
gathered by Mr. Jenner they are large, and on the
margin produce a dentate appearance.” •— R a fs .
5. T r i g o n o c y s t i s g r a c i l i s Hass.
Plate L X X X V . Eig. 1.
Char. Fronds muricated, deeply constricted in the centre, tioo
or three times longer than hroad, tapering on each side into
a slender process, which is terminated by three minute teeth.
End view triradiate.
Euastrum No. 13. Bailey, in American Bacillaria, pi. i.
fig. 2—5. Staurastrum gracile Ralfs, in Annals, vol.
X V . pi. xi. fig. 3.
Hab. Boggy pools, Dolgelly, and Penzance: Mr. Ralfs.
Although but three processes or teeth usually present themselves
to the observer, the real number is fo u r; but this is only
to be seen when one of the angles or rays is so situated tha t
its extremity is directly presented to the observer.
6. T r i g o n o c y s t i s ? a c u l e a t a Ilass.
Plate L X X X IV . Fig. 12.
Char. Fronds spinous. Segments in the front view, with a
process on each side terminating in three minute spines.
End view triangular, loith concave sides,
fl End view quadrangular, with fo u r distorted rays.
Staurastrum aculeatum Menegh., Synops. Desmid. p. 226.
Desmidium aculeatum Ehr., Infus. p. 142. t. 10. fig. 12.;
Ralfs, in Annals, vol. xv. pi. xi. fig. 4 .; Jenner, in loc.
cit. p. 194.
Hab. Cross in H a n d ; Sussex, and Beckley F u rn a c e :
Mr. Jenner. Penzance: Mr. Ralfs. — fl. Woking Common,
Surrey, and Piltdown Common, Sussex: ilfr.
Jenner. Penzance: Mr. Ralfs.
The spines are larger and longer in this than in any other
species of the genus. The variety, which I have not seen,
would appear to be referrihle to the species proper, and is
therefore very interesting.*
Section ii. S t a u r a s t r u m Ehr.
Char. End view quadrangular, often four-rayed, rays o f one
segment diverging from those o f the other.
Derivation. From aravpos, a cross, and aarpov, a star.
1. S t a u r a s t r u m d i l a t a t u m Ehr.
P late L X X X V . Fig. 5.
Char. Frond rough, deeply constricted in the centre. Segments
twice as hroad as long, obtuse at the sides, and not
elongated into processes. End view quadrangular. Angles
obtuse, sides excavated.
Ehr. Die Infus. p. 143. t. 10. fig. 13.; Menegh. Synops.
* Is not the normal number of ra}'s in this species four, and is it not
therefore a Stmiraatruin ?
A A