GuEviLLE, on New Diatoms. 
25 
and each apex there are from six to nine. The valve is the 
viewwhich occurs most frequently, and strongly resembles a 
Ceratoneis, there being an oblong inflation or expansion in 
the middle^ which passes suddenly into the long^ exceedingly 
narrow, subacute arms. The processes above described ap- 
pear in the view of the valve as strong, brilliant puncta, 
seated on one of the margins ; but the puncta which occur 
in the centre or inflated portion (nearly -0004" in breadth) 
are situated- more or less in the middle of the space, and not 
on the margin. 
Synedra. 
Synedra clavata, n. sp., Grev. — Valve broadly club-shaped, 
with an obtusely elliptical apex ; striae coarse, interrupted by 
three longitudinal lines. (Fig. 4.) 
Hab. Barbadoes deposit, Cambridge estate; in slides com- 
municated by C. Johnson, Esq. 
The striation of this fine species is extremely like that of 
S. robiista. Of the three longitudinal lines one runs up the 
middle, the others near the margin. The striae are about 15 
in *001^^ Length of frustule '0080'"; breadth at widest 
part '001 5'^ It is an extremely rare diatom, not more than 
four or five specimens having occurred in the hundreds of 
slides I have examined. 
COSCINODISCUS. 
Coscinodiscus Mossianus, n. sp., Grev. — Large; valve very 
convex, umbilical cellules loosely arranged, those of the cen- 
tral portion of the disc very large, roundish, irregularly 
radiant, becoming somewhat smaller, quadrangular, and 
symmetrically radiant towards the margin, within which 
they terminate in a crenate line. (Fig. 22.) 
Hab. Barbadoes deposit, Cambridge estate; C. Johnson, 
Esq. 
One of the finest species of this exquisitely beautiful genus 
which I have ever seen ; and so well marked that the charac- 
ters above given will be sufiicient to distinguish it in a 
moment. Nothing can be more beautiful than the sym- 
metrical radiance of the parts towards the margin, or the 
regularity of the crenate termination of the lines of cellules. 
I do not perceiA^e any trace of puncta or strise. The diameter 
of disc is -0062'" ; the lines of cellules at the margin, 5 in 
•001'". It gives me much pleasure to dedicate one of the 
most attractive of Mr. Johnson's discoveries to his friend 
