4 
Grbville^ on New Diatoms. 
connecting processes about 8; aculeate, situated near the 
suture. (Fig. 11.) 
Hab. Barbadoes deposit, Cambridge estate; in slides 
communicated by C. Johnson, Esq. 
Although I have been familiar with this little species for 
some years, I have refrained from its publication until I 
could quite satisfy myself that it was constant to its cha- 
racters. An extensive series of individuals having now 
passed under my observation, I no longer hesitate to admit 
its claims. Its ellipsoidal form and acute prominent suture, 
with the circle of aculeate processes arising at a short dis- 
tance from the suture, constitute an assemblage of cha- 
racters which cannot fail to identify it. The cellules are 
5 — 6 in '001'^ Diameter nearly always about -0020''. 
Cresswellia sphcerica., n. sp., Grev. — Minute ; frustules 
spherical ; cellulation very minutely punctiform ; connecting 
processes numerous, truncate, forming a terminal coronet. 
(Pig. 12.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides 
communicated by C. Johnson, Esq. 
Distinguished by its small size ('0010'' in diameter), its 
globular form and very minute cellulation, the cellules 
being as many as about 12 in '001'^ Although very rare, I 
have seen, at least, a score of specimens, but only a single 
example of frustules in connection. The processes are very 
slender and numerous, and are arranged in a diverging circle. 
Cresswellia minuta, n. sp., Grev. — Very minute ; frustule 
oblong, with rounded ends ; cellulation exceedingly minute. 
(Fig. 13.) 
Hab. Barbadoes deposit, Cambridge estate; in slides 
communicated by Mr. C. Johnson ; very rare. 
The length of this, the smallest species of the genus, is 
•0010'', the breadth -0005''. The connecting processes being 
more or less injured, I am unable to say whether they are 
truncate or aculeate. 
LiRADiscus, n. gen., Grev. 
Frustules simple, discoid (circular or oval) with a narrow 
connecting zone ; valves somewhat convex, sinuato-reticulate, 
more or less hispid. 
The objects of which I now venture to constitute a new 
genus, have long been a source of perplexity to me. Sometimes 
I have even doubted whether they were diatoms at all ; but 
have at length come to the conclusion that they have, at 
least, more right to be included in the family than the 
