I, :
:
11!
1 f a r
M
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Ilab. Gardener Street ; Air. Jenner.
Tlirough this and the following species the genus Navicula
seems to” pass into that of Cymhella, in which genus indeed
the striated Navicula would not be very improperly placed.
7. N avícula gibba Ehr.
Plate C II. Fig. 4.
Char. ■ Frustules ¿relatera! view straight, narrow, inflated; near
the centre gibbous.
Navicida gibha, N. unciata, Abhandl. der Akademie d.
Wissensch. zu Berlin, 1830, p. 64, 65. 68. 1831, p. 80.
Frustulia incrassata Kiitzing, Linnæa, 1833, p. 545.
t. xiii. fig. 17. Navicida gibba. Die Infus. p. 184. t. xiii.
f. 19. ; Jenner, in F l. of Tunbridge Wells, p. 204.
Ilab. Cheshunt: A .H . II. Ashdown Forest : Ja ck ’s
Wood Spring ; Chiltington Common, near Pulborough,
&c. : AAr. Jenner.
8. N avícula lanceolata Ehr.
P late C II. Fig. 14.
Char. Frustules lanceolate, extremities suhacide.
Frustulia lanceolata Kiitz., in Linnæa, 1833, p. 14. t. xiii.
f. 13. Navicida lanceolata Elir., Die Infus. p. 185.
t. xiii. fig. 21.
Hah. Sussex : Air. Jenner.
A well-marked little species.
80. E X IL A K IA Grev.
Char. Frustules elongated, at fir s t attached by a sessile and
undivided stipes, subsequently free, radiated, single, or binate.
Junction surfaces/reçMereZZy striated.
Derivation. From exilio, to issue forth ; in allusion to the
radiate disposition of the frustules.
433
This genus bears a slight resemblance to Gomphonema, the
frustules being attached in the young state of the species;
they are not, however, triangular, as in the genus Gomphonema.
1. E xilaria capitata.
Plate XCVII. Fig. 1.
Char. Frustules large. Tn front view truncate at the ends;
in side view dilated at both extremities into an obtusely
pointed head; striated.
Ehr. Die Infus. p. 211. pl. xxi. fig. 28.
This fine and beautiful species I found growing in immense
quantity in some ditches running parallel to the Barge
river near Cheshunt marshes. A few frustules of it have
also, I believe, been found by Mr. Ealfs. The frustules in
the front view are not to be distinguished from those of
Exilaria ulna; the side view of E . capitata is, however, so
distinct, that it would be impossible to confound it with that
species.
2. E xilar ia U lna.
Plate XCVII. Fig. 2.
Char. ^ Frustules large in the fu lly developed state. In front
view slightly dilated at the extremities, and truncate ; in
lateral aspect striated, extremities pointed.
Leuwenhoek’s Philosophical Transactions, 1703 (1702),
fig. 8. L. K. Bacillaria ulna Nitzsch, Beiträge zur
Infusorienkunde, 1817, p. 99. t. 5. Bacillaria communis
Bory, in Diet. Class. 1822. Frustulia obtusa and.
F. ulna Agardh, Consp. Crit. Diatom. Echinella fa sc iculata
ß truncata Greville, 1823; Scot. Crypt. Fl. 1.
t. xvi. Exilaria fasciculata Greville, 1827 ; Scot.
Crypt. Fl. V. f. 291 b. E . truncata Kiitz., in Linnæa,
1833, p. 560. Frustulia Ulna Harv., in Manual, p. 204.
E P