Greville^ on New Diatoms. 4-1 



A very small species compared with the preceding, but 

 evidently closely allied to it, the prominent character of the 

 scattered central puncta being distinctly exhibited in Ehreu- 

 berg^s rude figure. The small number of rays at once 

 separates it from all the others. 



Stictodiscus Johnsonianus , n. sp., Grev. — Pore-like puncta 

 of each compartment equal, forming a short linear series; 

 rays 50; diameter -003^". (PI. IV, fig. 3.) 



Hub. Deposit at South Naparima, Trinidad; Christopher 

 Johnson, Esq. 



Not less beautiful than Stictodiscus Buryanus, and well 

 distinguished by the single series of puncta in each compart- 

 ment, which extends from the margin to about a third of the 

 distance between it and the centre. Other puncta are scattered 

 over the surface of the disc, as in the two previous species. A 

 single example only has been found, for the possession of 

 which I have again to acknowledge the kindness of Mrs. 

 Bury. 



Stictodiscus insignis, n. sp., Grev. — Cellules large at the 

 margin, forming a moniliform series in each compartment to 

 near the centre; rays 46; diameter •0021". (PL IV, fig. 4.) 



Hab. Barbadoes deposit ; very rare, 



A small but exquisite diatom, of which I have as yet only 

 seen two individuals. It will be at once recognised by the 

 puncta, or in this instance rather cellules, which, commencing 

 at the margin, continue in a moniliform series, and de- 

 creasing gradually in size until they approach the centre, 

 when they lose their radiating character and occupy the entire 

 surface. 



In this species we do not find the peculiar puncta scattered 

 over the central portion of the disc, so characteristic of the 

 three preceding species, while the centre itself is fully occu- 

 pied with puncta or minute cellules similar to those of the 

 compartments. The valve is also much less convex. 



Stictodiscus dives (Ehr.), Grev. — Pore-like puncta in each 

 compartment minute, equal, forming a single series ; rays 52 

 (centre minutely punctate V). 



Discoplea? dives, Ehr. 



Actinoptychus dives, Ehr. 'Microgeol,' Pi. xix, fig. 12 ; Ralfs 

 in Pritch. ' Infus.' 4th ed., p. 840. 



Cyclotella dives, Kiitz., ' Sp. Alg.,^ p. 20. 



Hab. Egina. 



The appearance of this disc, as far as we can judge from 

 Ehrenberg's figure, is sufficiently striking to justify its pro- 

 visional admission into the genus. No central punctation, 

 however, is exhibited in the figure, 



VOL. I. — NEW SER. d 



