DoNKiNj on Marine Diatomacea. 
17 
II. Species new, or new to Britain ; first discovered by Pro- 
fessor Gregory in the estuary of the Clyde. ^ 
Campylodiscus simulans, Greg. Trans. Micr. Soc./ vol. v^, 
PI. 1, fig. 41) . — This species occurs in Druridge Bay^ but is 
somewliat scarce ; it appears to me to be a genuine Campylo- 
discus. Tbe valves^ in all the specimens in my gatherings 
are orbicular and saddle-shaped ; the median or central space 
is oval, with truncate extremities reaching nearly to the 
margin ; it is marked transversely with parallel lines from 
side to side, and it^ long axis in one valve is at right angles to 
that of the same space of the opposite ; the centre of the entire 
frustule thus presents a finely fenestrated appearance when in 
a certain focus, owing to the crossing at right angles of the 
transverse lines of the two opposed spaces. In these respects 
it differs widely from Surirella fastuosa and lata, of which 
Professor Gregory thinks it may be a variety. 
Coscinodiscus concavus, Ehr. (Greg., Clyde Forms,^ pi. ii, 
fig. 47). 
Frcqnent along the coast. 
Navicula granulata, Breb. — The form of this species varies 
widely, from being in some specimens nearly orbicular to 
linear, or linear constricted in others ; the extremities being 
always obtuse and produced. The striae are coarse and widely 
punctate, but always uniform. It cannot be confounded with 
N. humerosa, Breb. {quadrata, Greg., ^ Trans. Micr. Soc.,^ 
vol. iv, PI. V, fig. 5), which also varies much in outline, by 
the most careless observer. As both forms were abundant 
in some of my gatherings, I have had an opportunity of com- 
paring hundreds of specimens. f 
Hab. Cresswell and Linemouth, abundant. 
Navicula latissima, Greg. {' Trans. Micr. Soc.,' vol. iv, 
PI. V, fig. 4). 
Frequent at Linemouth. 
* I have satisfied myself tliat all the species enumerated under this head 
occur on the Northumbrian shore, having carefully compared specimens with 
those contained in series of slides, kindly sent to me by Professor Gregory, 
illustrative of all his new Clyde forms. 
I may also mention that, independent of these, I have detected several 
other species found in the Clyde, of which Professor Gregory intends shortly 
to publish a description. I have therefore not alluded to these in this 
paper. 
f I have thought proper to give two figures of this large and beautiful 
species (fig. 19, a and b)^ to show how much it varies in its outline. The dry 
valve, when seen with a low power, is of a dull bluish colour, inclining to 
purple; while that of N. humerosa is colourless and hyaline. 
