SCHULTZE, ON DIATOMACEZ. 21 
The Diatoms shown in figs. 11 and 12 must be referred to 
the genus Denticella, if we consider Ehrenberg’s D. amita 
(‘ Microgeologie,’ tab. xxx, A, figs. 2, 3, 7) asthe typical form. 
They agree very closely with the form named by Bailey 
Zygoceros (Denticella?) mobiliensis (‘‘ Microsc. Observ. made 
in South Carolina, Georgia, and Florida,” ‘Smithson Contrib.,’ 
vol. ii, p. 40 of the separate copies, tab. 11, figs. 84 and 35), 
which cannot be, however, a Zygoceros, but is a true Denticella, 
as Herr J. Miiller informed me in reply to an inquiry 
respecting his opinion. One might impute the difference 
from our species to the inaccuracy of Bailey’s somewhat 
rough drawing. The size Bailey does not mention. The 
specimen given in fig. 1] measured 0°11” in length (without 
the prickles), and 0:065'” in breadth. That in fig. 12 was 
0°125'” in length, and 0:098” in breadth. The lengths of the 
individual sprouts of division were 0:055 and 0:065'"; it was 
thus much less than their breadth, which, in connexion with 
the other measurements already given, presents a great 
variety in form. Young specimens, at first released by the 
division, sometimes appear broader than they are long, at 
others longer than they are broad. Besides, there occurred 
at Heligoland much smaller Denticelle, which (either the 
young of our species or of a new one) appeared to have 
originated in a different manner than by division. The cross- 
cutting of our Denticella is barley-corn shaped, and ends 
naturally above and below in two external projections. The 
spines are placed internal to the projections, not in the two 
lines uniting the projections to one another, but the one to 
the right and the other to the left of them. Hence the 
uneven appearance the one has compared with the other in 
the two individuals caught in the act of dividing (fig. 12). 
In water the siliceous coat appeared destitute of all finer 
structure. With great pains two cross lines can be perceived, 
running parallel to each other, which are shown in our 
drawings. These are always at the same distance from the 
upper and under ends, and approach more closely to one 
another the shorter the individual. After the application of 
a red heat, and by the use of oblique light, there is brought 
into view a fine hair-like marking of the surface, as seen in 
Navicula angulata. Such a fine clothing D. mobiliensis of 
Bailey, from the coast of Florida, shows. After all the 
information given, our Denticella will be easy again to recog- 
nise. I have named it Denticella regia. 
