Greville, on New Diatoms. 78 



Cocconeis granulifera, n. sp., Grev. — Minute^ elliptic- 

 oblong;, with a median line and rather large nodule ; disc 

 witli remote radiating lines of large, oval granules (three in 

 each line), reaching from the median line to the margin. 

 Radiating lines 5 in -001". Length -0015". (PI. VIII, fig. 19.) 



Hab. On Pectens, Carrickfergus ; John Grant, Esq. 



The characteristic features of this little species are the very- 

 large granules, the small size of the valve being considered 

 (three only being found in each line), and the distance 

 between the radiating lines themselves, there being only 

 about thirteen on each side. Both this and the preceding 

 appear to be clearly distinct from all described species. 



Descriptions of New and Rare Diatoms. Series III. 

 By R. K. Greville, LL D., F.R.S.E., &c. 



(Read June 12tli, 1861.) 



Brightwellia, Ralfs. 



BrigJitwellia eJaborata, n. sp., Grev. — Cellules of coronal 

 circle roundish ; border composed of uniform, radiating lines, 

 connected by numerous transverse lines. Diameter -0034". 



(PI. IX, fig. 1.) 



Hab. Barbadoes deposit ; excessively rare. 



This exquisite diatom bears a considerable general resera- 

 blance to Brightwellia Johnsoni of Ralfs, MS., being of the 

 same size and having a very similar coronal circle of large 

 cells. But an essential difference is found in the structure 

 of the border. In B. Johnsoni it is composed of radiating 

 lines of round cellules, which decrease in size from the corona 

 to the margin, where they are quite minute; while at irregular 

 intervals dark, strong, radiating lines occur, which appear to 

 project like a spinous ridge, as in my Coscinodiscus armatus. 

 In the present species, on the contrary, the border is formed 

 by a close series of straight, uniform, radiating lines, connected 

 by transverse (or concentric) lines or bars, which thus pro- 

 duce rows of quadrate cellules, increasing in size from the co- 

 ronal circle to the margin. Two of the radiating lines, with 

 their connecting bars, might not unaptly be compared to a 

 microscopic ladder. 



