3 Dr. R. K. Greville on new Genera and 



ture and intermediate ring-like zone. Nevertheless the minute 

 organization is very similar ; for we have an hexagonal cellulation 

 radiating from a centre, along with a series of other sharply 

 defined lines, which may be called radiating costse, and which 

 terminate in submarginal nodules — the analogues of the lines 

 and minute spines in Coscinodiscus concinnus of Smith. But 

 our new Diatom seems, at first sight, to have a closer affinity 

 with Dr. WallicVs curious genus Hemidiscus, which at present 

 is placed (I fear erroneously) among the Anguliferece. The 

 arcuate form, radiating cellulation, and submarginal puncta 

 certainly show an approximation between the two. Whatever 

 view, however, may be taken of their family relations, there are 

 differences which must keep them apart as genera — the chief of 

 which is the nodule on the ventral margin of Hemidiscus. The 

 submarginal puncta in that genus are also very different from 

 the minute nodules which terminate the radiating costse in Pal- 

 meria ; and it is not unworthy of notice that the point of radia- 

 tion in the latter genus is never exactly centrical, being invariably 

 somewhat to the ventral side of the centre ; whereas in Hemi- 

 discus it is truly centrical. 



In a popular view, the frustule of Palmeria is graphically 

 compared by its discoverer to the half of a peeled orange, the 

 lines on the convex surface representing the segments of that 

 fruit. 



In the living state, the endochrome is collected into minute 

 roundish masses, which dot the whole of the interior of the 

 siliceous covering. The nucleus in the valve is then very con- 

 spicuous ; and I have a sketch, from Mr. Palmer, showing 

 radiating "reticulated cords," similar to those described and 

 figured by Professor Max Schultze in Coscinodiscus centralis and 

 his Denticella regia (Mic. Journ. vol. vii. p. 13, pi. 2. figs. 11-13). 

 This appearance has also been observed, even in this country, in 

 specimens received from China, both of Palmeria and of a spe- 

 cies of Coscinodiscus, by my friend Mr. Laurence Hardman. The 

 peculiar current-like motions described by Prof. Max Schultze 

 have been witnessed likewise to some extent by Mr. Palmer, 

 especially the formation of a more compact mass of active parti- 

 cles, changing both its shape and position within the cell from 

 time to time. (Letter, June 1864.) 



Palmeria Hardmaniana, n. sp., Grev. PI. V. figs. 1-4. 



Hab. Hongkong Harbour ; John Linton Palmer, Esq., Surgeon 



R.N., 1863. 



A very large Diatom (varying, however, greatly in size), some 

 examples being as much as '0160" and upwards in diameter. 



