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Derivation. From k o k k o s , a grain, and vyga, a thread.
The frustules in this genus may be compared to a grain of
wheat in form.
1. CoCCONEMA LANCEOLATUM Ehr.
Plate CL Fig. 1.
Char. Frustules large, semi-lanceolate, straight, obtuse.
Gomphonema lanceolatum Agardh, Conspect. Crit. Diatom.
1831, p. 34. Gomphonema {Paltonophora) lanceolatum
Kiitz., in Linnæa, 1833, p. 38. ; Jenner, in Flora of
Tunbridge Wells. Cocconema lanceolatum Ehr., Die
Infus. p. 224. pl. xix. fig. 6.
Hah. Waterfall at Hill Park, Westerham, and at Shoreham,
Kent; Parham, near Pulborough, &c. : Mr. Jenner.
Cheshunt : A. H. H.
This is a very fine and distinct species.
2. Cocconema cymbifoeme Ehr.
Plate Cl. Fig. 2.
Char. Frustules slightly curved, narrow, attenuated, suh-
acute.
FrustuliacymbiformisXütz., in Linnæa, 1833, p. 540. t. 15.
fig. 9. Cocconema cymbiforme Ehr., Die Infus. p. 225.
pl. xix. f. 8. ; Jenner, in Fl. of Tunbridge Wells.
Hab. New Elver reservoir, Cheshunt ; A. H. H.
This species might readily he confounded with the previous
one, from which it is to be distinguished by its smaller, narrower,
more attenuated and somewhat curved frustules.
3. Cocconema cistd la Ehr.
Plate Cl. Fig. 3.
Char. Frustules crescentic, ventricose, obtuse, often in pairs.
Cocconema cistula Ehr., Die Infus. p. 224. pl. xix. f. 7. ;
Jenner, in Fl. of Tunbridge Wells. Cymhella copulata
Breb. and Godey. N. geminata? Tui’p. (1828).
Hab. Frequent in Sussex: ilfn Jewwer. Cheshunt : A. D . D.
The frustules in this species are shorter than in those previously
described, more ventricose and obtuse. In C. lanceolatum
the frustules are straight, in C. cymbiforme but slightly
curved, while in C. cistula they are considerably so.
4. C occonema v e n t e ic o sa ? Hass.
P late Cl. Fig. 4.
Char. Frustules small, straight, ventricose, obtuse.
Cocconema? gibbum Ehr., Die Infus. p. 225. pl. xix. f. 9.;
Jenner, in Flora of Tunbridge Wells. Cymhella ven-
tricosa Ag. ? Flor. Bot. Zeit. ; Breb. and Godey.
Hab. Cheshunt: A. H. H. Waterfall at Harrison rocks:
ilfr. Jenner.
This is the smallest species of the genus which has hitherto
been described. From Cocconema phoenicenteron, with which
it might be confounded, it differs in size and in the frustules
not being curved.
78. C YM B E L LA ffess.
Char. Frustules cymbiform, striated, sulcated, not stipitate.
Derivation. The diminutive of cymba, a boat ; in allusion
to tlie form of the frustules.
This genus differs from Cocconema only in the frustules
not being stipitate as they are in that genus. Although not
stipitate, the frustules frequently are attached in the entire
length of their fiat surface to other Algæ, often to Clodo-
phora crispata. The Cgmbella of Agardh embraces species
belonging to several distinct genera, and not one of those here
described under the name of Cgmbella. The following are