I
Forfar, at an eleyation of 2800 feet. Near Aberdeen and near Belfast,
Dr. Dickie; Rcseobic, Mr. P. Grant. Marl, Co. Down, &c.
Plate III. 33. d. outline of ditto in S. V.
4. Cocconeis Scutellum, Ehr. V. orbicular or elliptical; striæ
concentric with extremities, moniliform, 18 in -001". Length
•0006" to -0016". v.v.
/3. Nodule dilated into a Stauros.
Ehr. Inf. xiv. 8. Kiitz. Bacill. v. 6.
Marine. Very common, and exceedingly variable in size and outline.
Plate III. 34. ¡i, Supp. Plate XXX. fig. 34.
5. Cocconeis Grevillii, n. sp. V. oval, furnished with transverse
canaliculi; striæ moniliform, 15 in -OOl". Length-0008" to -0025".
v.s.
Quek. H. C. pi. xii. 19 ?
Marine. Attached to Phyllophora rubens, Sidmouth, communicated by
Dr. Greville. Hastings, Mr. Shadbolt. Poole Bay, W. Sm. (Algoa Bay,
South Africa. Ichaboe Guano.)
Plate III. 35 a. lower valve ; 35 a*, upper valve ; 35 a'. Hew of upper valve
from within.
6. Cocconeis diaphana, n. sp. V. elliptical, scarcely siliceous, diaphanous
; striæ obscure. L en g th -0012" t o -0018". v.v.
Nodule dilated into a Stauros.
Marine. Sidmouth, Miss Cutler, communicated by Dr. Greville. Pontac,
Jersey, Aug. 8, 1852, W. Sm.
Supp. Plate XXX. 254.
G e n u s 6 . COSCINODISCUS, Ehr.
Frustules free or adherent, disciform ; valves plane or slightly convex
with a cellular structure.
This genu.s, though closely related to those which immediately
follow it, finds its nearest allies in the Melosirem, whose genera, from
their filamentous character, stand widely apart in the present work.
J
Were the frustules of Coscinodiscus eccentricus, for example, permanently
coherent after self-division, it would be difficult to separate
them in a generic point of view from those of Orthosira nivalis,
W. Sm., which have the same cellular structure of the siliceous valve,
or from those of Melosira aurichalcea, Ralfs, or Orthosira sulcata,
Kütz., which are furnished with a projecting fringe of silex, the
homologues of the spinous processes in C. eccentricus. It is true that
the Mdosirece I have mentioned have valves much more convex,
occasionally even cylindrical; but in Orthosira arenaria,W. Sm., this
difference disappears, and we have frustules as much compressed and
in consequence as narrow on the F. V. as in Coscinodiscus, and
differing principally in the firm and permanent coherence of their
surfaces.
1. Coscinodiscus minor, K/«-. C e l l s of V . circular, margin smooth.
V.S.
Ehr. in Kütz. Bacill. i. 12 ?
Fresh water. Aberdeenshire, Dr. Dickie.
Plate III. 36.
2 Coscinodiscus radiatus, Ehr. Cells distinctly hexagonal, arranged
concentrically, largest in the centre of valve, margin smooth.
Diameter -0018" to -0055". v.v.
Kütz. Bacill. i. 18. Prlt. Anim. xiv. 39.
Marine. Poole Bay, 1848. Stomach of Scallop, coast Sussex, IF. Sm.
Coast of Norfolk, Mr. Brightwell. Near Falkestoiie, Mr. Capron. (1 eruvian
and African Guano.) ' '
Plate III. 37.
3. Coscinodiscus eccentricus, Ehr. Cells arranged in eccentric
lines, margin spinous. Diameter -0006" to 0038". v.v.
Kütz. Bacill. 1. 9.
Marino or brackish water. Poole Bay, Aug 1848 Near Lewes, July
1850, Stomach of Scallop hi great luimhers, Feb. 18al.