68 
Greville^ 071 New Diatoms, 
This remarkable genus appears to belong to the group re- 
presented by Asterolampra, but differs essentially in the ab- 
sence of umbilical lines and of the hyaline area, so conspicuous 
in all the discs referred to that genus. In the only known 
species of the genus now proposed, the valve is cellulose, very 
much in the manner of Coscinodiscus radiatus ; and the rays, 
two in number, have their dilated bases separated by a con- 
siderable interval, and have no connection whatever with each 
other. This singular diatom is worthily dedicated to my friend 
Thomas George Rylands, Esq., of Heath House, Warrington, 
a very acute observer, w^ho communicated it to me soon after 
its discovery by Mr. Ealfs. 
Bylandsia biradiata, n. sp., Grev. (PI. VIII, fig. 1). 
Hab, Barbadoes deposit, very rare ; John R-alfs, Esq., T. 
G. Rylands, Esq., Dr. Greville. 
A considerable number of specimens of this curious disc 
have now been seen, and it is satisfactory to know that it is 
quite constant to its characters. The cellules in the centre of 
the valve between the bases of the rays are large ; they then 
suddenly become smaller, and decrease gradually in size as 
they radiate to the circumference. The rays are broadly 
cuneate at the base, and linear as they reach the margin ; 
they appear to be tubular, as in Asterolampra, and a faint 
shadow indicates the continuance of this structure through 
the middle of the dilated bases. In a single instance the two 
valves occurred in situ, the rays of the lower crossing those of 
the upper valve. 
Coscinodiscus. 
Coscinodicus symmetricus, n. sp.,Grev. — Granules radiating, 
distinct, all equal and equidistant ; seven of the radiating 
lines extending from the centrical granule to the circum- 
ference; margin striated. Granules 10 in -100 ' ; marginal 
stri« 15 in -001". Diameter -0031". (PI. VIII, fig. 2.) 
Hab, Barbadoes deposit ; excessively rare. 
One of the most beautiful of the granuliferous group of 
Coscinodisci, and well characterised by the equal distribution 
of the granules. It is also distinguished by the manner in 
which the radiating lines are arranged. From the central 
granule proceed seven long lines, and within the compart- 
ments so formed the next two longest are disposed, one on each 
side, so as to form two equal sides of the triangle, and so on 
until the whole space is filled up. 
Cresswellia. 
Creswellia superba, n. sp., Grev.— Valves hemispherical. 
