SCHULTZE, ON DIATOMACE. 19 
xxii, p. 94, and delineated in Plate V, fig. 5. The tubes 
are cylindrical, pretty abruptly pointed at both ends, and 
furnished at the extremity with a small siliceous point, ap- 
parently solid, or at least with very thick walls, sharply 
marked off from the cavity of the cylmder. The pointing of 
the species, according to various positions of the tube ob- 
tained by rolling it round, originates nearly like a cut-out 
quill-pen. The length and thickness of the tubes vary 
much. I have seen them from 0-4 to 0:7” Par. in length, 
and 0:025 to 0:04’" in thickness. The most examples are 
found in the act of division, which is in an oblique direction, 
while others consist of from three to six individuals cohering 
together. Of such I have measured several. A. Four co- 
herent individuals, 0°68", 0:42", 0:4", 0:46" in length. 
B. Three ditto, 0°7'”, 0°76, 0°68” in length. C. Three 
ditto, 0°72", 0°54'”, 0°52'” in length. D. Six individuals 
attached to each other, 0°52”, 0°74", 0:5", 0°52'", 0-5” in 
length ; the last was broken off; the entire length of the 
tube was 3’. Characteristic of R. styliformis are the ringed 
markings which the shell possesses. These appear not re- 
markable in water, but come out very sharply after subjec- 
tion to a red heat, or desiccation after previous treatment by 
acids. I have taken pains in fig. 4 to give a most correct 
drawing of the same, as they appear in that position of the 
Rhizosolenia which resembles a cut quill-pen, with the cut 
surface turned towards the observer. ‘The upper part of the 
two individuals shown in fig. 3, still hanging together after 
the division, turned round in its long axis towards the left 
about 90°, would then present the same view as fig. 4. The 
oblique falling-off side of the young ends is presented to the 
beholder. On it, im the middle, is found a design like the 
tip of a lance. It is, to look at, in a manner like an impres- 
sion of the once closely applied end of another individual. 
Here a confinement of the shell to the very last may take 
place during the division, perhaps even an aperture in the 
siliceous coat remains in the dark lines, a, a, which I could 
sometimes nowhere discover. The ringed markings of the 
shell are made by linear incisions, therefore the shell most 
commonly breaks in the rings. A wider and finer marking 
of the siliceous coat could not be discovered, either in the 
red-hot condition or by the use of oblique light. 
The second species, which is rarer in Heligoland, I have 
named R. calcaravis (figs. 5—8). It is smaller than the 
first, and occurs im solitary, not in numerous, individuals 
adhering together. Length 0°20'’—0°25'"; thickness, 0°025. 
Specimens of 0°25" already showed the oblique division in 
