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 stride 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 imibonate 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 ^dew. 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 above 

 recorded, he has observed this diatom in the Pescatawa}', 

 Rappahannock, and Monterey deposits. 



COSCINODISCUS. 



Coscinodiscus patellcefonnis, 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 

 gi'anules increasing in size to the circumference; margin 

 with a row of minute puncta. Diameter about •0034". 

 (Fig. 4.) 



Hab. Barbadoes deposit ; very rare. 



This curious diatom has much the appearance, under a 

 low magnifjdng power, of Coscinodiscus biradiatus, 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 Patellce. The 

 last-mentioned series, or, as they may be called, the coronal 



