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96 TERMINOLOGY AND CLASSIFICATION OF DIATOMS.
FAMILY (III.)
NAVICULACE^E.
Frustules with similar f Valves elliptic with a projecting keel .
valves, asymmetrical - ..... , , ,
about both axes I Valves sigmoid, without keels or alas
Fiustules with similar f
valves, symmetrical -l Valves naviculoid, without keels or a.\x.
about both axes . L
Frustules with similar f Valves elliptic, with marginal aloe and
valves, symmetrical i robust costaa ....
about the major axis . Valves linear, without alas or keels
j^
Frustules with similar f
valves, symmetrical 4 Valves arcuate ....
about the minor axis .
(..
Sub-Order (B.) COCCOCHROME^E.
Family (IV.)
TABELLARIACE/E.
Frustules rectangular f Frustules rectangular. Valve view generor
cuneate, furnished | an y elliptic, never cuneate
with diaphragms or A ,
Frustules
semi-diaphragms
and valves
parcuneate,
valve view
allel to' the valves cuneate .....
. I
Frustules cylindrical, consisting of plates united by their margins and
terminating in conical or pointed valves ....
Family (V.)
FRAGILARIACLE.
Valves linear, elliptic, constricted or sometimes cuneate; striate'
transversely, without nodules or raphe
....
....
Valves elliptic, punctated with coarse puncta, often quadrate with
hyaline spaces at the centre and apices
Valves always cuneate with coarse puncta, often quadrate or with slits
like buttonholes. No hyaline space at the centre .
Family (VI.) CH.ETGvRACE/E.
Tribes.
5. Amphiprorese.
6. Pleurosigmeae.
7. Naviculese.
8. Surirellese.
9. Synedrese.
10. Eunotieae.
11. Tatoellarieae.
12. Licmophoreae.
13. Rhizosoleniese.
14. Fragilariese.
il. Plagiogrammeae.
16. Trachysphenieae.
Valves rounded or elliptic, furnished with long filaments 17. Chsetocerese.
Family (VII.)
BIDDULPHIACE.E.
Valves polymorphous, triangular, quadrate, polygonal, sometimes
elliptic, never discoid, often furnished with spines
Family (VIII.) COSCINODISCACE^E
Valves discoid, sometimes elliptic, furnished with one or more marginal
ocelli or projecting tubercular processes
Valves discoid, divided (following the course of the radii) into sections
alternately light and dark ......
Valves discoid with a central hyaline area connected by hyaline furrows
to marginal ornate compartments
. 18. Biddulphiese.
....
.....
Valves discoid, sometimes elliptic, with surface covered with areoles of
beads arranged in lines radiate, transverse or vertical, or well
divided in concentric zones with different markings
Family (IX.) MELOSI RACEME.
Valves discoid, very convex, furnished with marginal spines. Frustules
globose ........
Valves discoid, flat or
slightly convex, sometimes furnished with small
spines on the surface. Frustules cylindrical, often united into
cylindrical filaments . .....
19. Eupodiscese.
20. Heliopeltese.
21. Asterolamprese.
22. Coscinodiscese.
23. Xanttaopyxideae.
24. Melosirese.