ROPER, ON BRITISH MARINE DIATOMACES. 19 
these gatherings of which the characters are so doubtful that 
it is impossible to determine satisfactorily their specific, or, in 
some cases, even generic position. All the drawings are mag- 
nified 400 diameters. 
Eupodiscus tessetatus, n. s.—Cellular structure distinctly 
hexagonal, with a small rounded nodule at each angle of the 
hexagons. The surface of the valve slightly elevated, flat, 
with a declining margin, of about one fifth of the diameter ; 
pseudo-nodule single, submarginal.- Colour of dry valve 
brown. Diameter :002”; diameter of cellules -000066" (fig. 
i avand 6,'Pl: 111). 
Marine. Caldy, Pembrokeshire, Rev. J.Guillemard; Hum- 
ber, Mr. Norman. 
I received the first specimens of this very pretty species in 
a gathering obtained by the Rev. J. Guillemard, by washing 
a collection of small Algze, from the shore of Caldy Island, 
near Tenby, and have since met with it im some slides sent by 
Mr. Norman from dredgings in the Humber. It belongs to 
the same class as H. crassus, fulvus, and Ralfsii ; which differ 
from HE. argus, the typical species, m having merely one 
circular spot or pseudo-nodule near the margin, and not dis- 
tinct processes, as in that species. The cellular structure is 
very peculiar, and unlike any other Diatom that I am ac- 
quainted with, excepting coscinodiscus concinnus, each angle 
of the hexagons bemg marked with a small dot or boss, as 
shown in fig. 1 0, requirmg a magnifying power of 800 to 
1000 diameters to bring out distinctly. The valves, when 
seen with a low power, have so much the appearance of a 
small piece of mosaic that I have named it ¢esselatus. 
This species differs from EH. radiatus, the only form with 
hexagonal cells, placed, I thik doubtfully, in this genus by 
Professor Smith, in the peculiar arrangement of its cellules, 
and in wanting the elevated processes and spines, which would 
rather lead me to place that species with the Biddulphias 
than in its present position.* 
* Professor Smith, at p. 47 of the second volume of the ‘Synopsis,’ 
alluding to this species, states that it differs from Biddulphia ‘in the orbi- 
cular outline of the valve, and in the processes being rather projections 
from the disc than produced angles.” I have, however, specimens of B. 
turgida, which are very nearly orbicular, and I cannot agree that the pro- 
cesses simply rise from the surface of the disc, as shown in t. lxii, f. 255, 
of the ‘Synopsis,’ but are projections rising gradually from the centre of the 
valve, with cellular structure continnous nearly to their apices, exactly as in 
B. rhombus, many specimens of which are also nearly orbicular. In addi- 
tion, the processes in Eupodiscus are all similar in structure, whilst in Z. 
radiatus we have two cellular projections, and two spines, as in B. Baileyit, 
and generally in B. aurita. 
