80 
Greville_, on New Diatoms. 
Hah. Nottingham deposit^ Maryland, U.S. ; Richmond, 
Virginia, F. Kitton, Esq. 
A small but beautiful species, with very numerous puncta 
of equal size throughout, and especially distinguished by the 
umbonate surface and central nucleus of the disc. The rays 
terminate simply at the margin, which is unmarked by 
puncta or striae of any kind. My best thanks are due to 
Mr. Kitton for a specimen exhibiting the front view, which 
forms a very interesting object. It shows the frustule to be 
composed of two unequally umbonate valves, each of them 
furnished with a broad, folded-down edge, as in the lid of a 
pill-box, which edge is divided into large, square cellules, 
corresponding in number with the rays and compartments as 
seen in the side view. These cellules are the more con- 
spicuous from being destitute of any kind of sculpture. Mr. 
Kitton informs me that, in addition to the localities abovfe 
recorded, he has observed this diatom in the Pescataway, 
Rappahannock, and Monterey deposits. 
COSCINODISCUS. 
Coscinodiscus patellceformis, n. sp., Grev. — Central granules 
minute, round, numerous, from which proceed a number of 
rays, terminating about half way between the centre and the 
margin in an irregular circle of minute, dark, spine-like 
tubercles, beyond which are radiating lines of sub-contiguous 
granules increasing in size to the circumference; margin 
with a row of minute puncta. Diameter about •0034". 
(Fig. 4.) 
Hah. Barbadoes deposit ; very rare. 
This curious diatom has much the appearance, under a 
low magnifying power, of Coscinodiscus hiradiatus, with some 
adventitious matter adhering to the disc. Indeed, I passed 
over several specimens under this impression ; but I was at 
length induced to examine them more carefully, and per- 
ceived that several important characters indicated a distinct 
species. The radiating lines which occupy the outer half of 
the disc are composed of coarse granules almost touching one 
another, and increasing in size as they approach the margin. 
But a more remarkable feature is found in another series of 
radiating lines, occupying not exactly the centre, but what 
may be termed the crown of the disc, and terminating about 
half way down. These have all the appearance of a separate 
structure, closely united to the original one, the whole 
bearing a strong resemblance to some of the PatellcB. The 
last-mentioned series, or, as they may be called, the coronal 
