6 
LaudeRj on Neio Diatoms, 
with enumerating : their defects, or their degrees of merit,, I 
must leave to those who have had more experience than my- 
self in the examination of objects under compression; but in 
ElG. II. 
my very limited observations I have frequently felt the want of 
some means of reversing the object quickly and easily whilst 
under pressure. 
On New Diatoms. By Henry Scott Lauder, Assistant- 
Surgeon Eoyal Navy, H.M.S. " Melville.'' 
(Communicated by Dr. Lankester, F.R.S.) 
Family Chactocen^. 
Genus Bacteriastrum. 
Filamentoits ; usually having about twenty frustules in the 
filament ; connected together by the intimate apposition of 
the awns of contiguous cells for a part of their length; 
cylindrical ; side view discoid al, with from five to thirty-two 
awns radiating from the margin of the disc ; those of the cells 
at each extremity of the perfect filament are more or less 
simply curved, and their origin is slightly submarginal. The 
intermediate awns present the appearance of being bifurcated 
for about half their length. This appearance is caused by 
the awns of contiguous frustules being closely approximated, 
or, as it were, blended together for a certain distance from 
the margin of tlie cell, and for the remaining part of the awn 
to the extremity they separate into the two awns of which 
•|;hey are primarily composed, belonging to different frustules, 
