8 
Greville, on New Diatoms, 
and size, and from having been found in a free state in 
deposit or guano^ have been very often mistaken for 
distinct species of diatoms by many observers; among these 
may be mentioned Dicladia, Eonisthecium, Hercotheca, 
&c. &c., all of which are the bodies formed within the 
frustules of diatoms belonging to Chactocerea3. 
Species 1. 
Bacteriastrum vay^ians (figs. 1 to 6). Breadth of frustule 
more commonly j number of awns usually from ten to 
thirteen; those of terminal frustule slightly submarginal^,^ 
intermediate awns marginal. Very common^ floating freely 
in Hongkong harbour. 
Species 2. 
Bacteriastrum hyaliniim (7 a, b) is distinguished from the 
former by being very hyaline, and having constantly thirty 
or thirty-two awns, B, varians never having more than 
twenty-four. 
Body of frustule is short in front view, and is constantly 
in diameter ; length of awn about twice and a half the 
diameter of the disc ; found under the same circumstances 
as B, varianSj but not so common. 
Descriptions of New and Kare Diatoms. Series XI. 
By H. K. Greville, LL.D., F.H.S.E., &c. 
(Communicated by F. C. S. Roper, F.L.S.) 
Terebraria, nov. gen., Grev. 
Frustules in front view quadrangular, binately conjoined, 
with transverse rows of conspicuous pseudo-pores, and a longi- 
tudinal serrated sutui'e. Yalve elliptical, with transverse rows 
of similar pseudo-pores. 
This highly curious fossil genus is conspicuous at first 
sight for the large, distinct pores, or pseudo-openings, arranged 
in rather distant rows, and, on a closer examination, for the 
sutural line being serrated, a character which, as far as I 
know, has not been observed in any other diatom. In the 
* The terminal disc has a distinct central punctum. 
