ORIGINAL COMMUNICATIONS. 
Descriptions of New and Rare Driatoms. Series X. 
By R. K. Grevitiz, LL.D., F.R.S.E., &c. 
(Plates IX and X.) 
RvuTiLaRiA, nov. gen., Grev. 
Frustrotes free, elongated, compressed, with a convolute 
or nodulose central nodule (no median line or terminal 
nodule), and minute radiate or decussato-punctate structure. 
Valve (linear, keeled?) with a longitudinal row of puncta. 
This is a most remarkable fossil genus, and its systematic 
position exceedingly perplexing. I have reason to believe 
that Mr. Kitton, of Norwich, who kindly sent me his cabi- 
net specimens for examination, was the discoverer of the 
first species, which he obtained from the Monterey deposit, 
and named provisionally Nitzschia Epsilon, on account of the 
resemblance of the nodule to the Greek letter. But this 
nodule, conspicuous for its glistening appearance, as well as 
for its singular convolution, appeared to me to separate it 
from Nitzschia. Unfortunately no single valve occurred 
among the specimens found by Mr. Kitton and myself; and 
being unable with the instruments then in my possession to 
satisfy myself regarding the structure, I sent the specimens 
to my friend Mr. T. G. Rylands, who ascertained that the 
frustule was really Nitzschoid, in so far that the valves were 
keeled and furnished with a row of puncta. Still, the ex- 
traordinary nodule forbade its association with the true 
Nitzschie, aud I laid the subject aside until further informa- 
tion could be obtained. 
Recently two other diatoms have been discovered by Mr. 
C. Johnson in the Barbadoes deposit, which are evidently 
VOL. I1I.—NEW SER. R 
