ew ea aS 
NEW FORMS OF MARINE DIATOMACEZ. 529 
101. Navicula (?) Libellus, n. sp. Pl. XIV., figs. 101, and 101 6. Form of F.V. 
rectangular, broad, with the angles rounded. The middle part is marked by lon- 
gitudinal lines or folds, like the leaves of a book; and when the two halves of the 
F.V. separate, each retains a broad band of this lineate part. The breadth of 
the detached halves on the F.V. is so great, that, when united, they must, it 
would seem, mutually overlap, otherwise the resulting frustule would be much 
broader than it is. §S.V. rhombic or elliptic-lanceolate, broad, with obtuse ends. 
Length from 0-003’ to 0-0035"; breadth of F.V. 0:0017’ to 0-002’. The S.V. is 
marked by very fine transverse striz; striz about 60 in 0-001"; median line 
distinct; nodule definite. When the edge of the S.V. is seen, as in fig. 101 8, 
the valve seems to be a compound one, formed of five or six, closely packed one 
over the other. I cannot ascertain if this be so or not. 
This species is frequent in Lamlash Bay, and it much resembles the form 
figured by me in my second plate from the Glenshira Sand, under the name of 
N. rhombica, of which also I had figured two of the S.V. in my first plate (Zrans. 
Mic. Soc., vol. iv., pl. v., fig. 1, and Mic. Jour., vol. iii., pl. iv., fig. 16). But I 
observe several uniform points of difference. WV. Libellus is more obtuse and broader, 
and its striation is not only much finer, but the strive are everywhere of uniform 
size and at a uniform distance; whereas in NV. rhombica, they are near the middle 
of the valve, not only stronger, but so much more distant than in the rest of the 
valve as to be almost conspicuous. J. Libellus is also, on the whole, a larger 
form than WV. rhombica. 
But it is very doubtful whether either of them be really a Navicula. They 
have some resemblance, especially on the F.V., to Schizonema Grevillii, Sm., 
which, however, is a much smaller form. Still they may possibly belong to 
Schizonema, but this cannot be ascertained except in living, or at least quite 
recent and uninjured specimens. The F.V., with its foliated or complex struc- 
ture, appears to me, however, to differ from that of a Schizonema. 
I may here add, that there occurs in Lamlash Bay a much smaller form of 
the same shape, but not foliated, at least not distinctly so. This is perhaps the 
true S. Grevillii. 
102. Nitzschia (?) panduriformis, nu. sp. Pl. XIV., fig. 102. Form linear, 
broad, incurved in the middle, acuminate at the ends, which are usually obtuse 
and rounded, but sometimes acute and sub-apiculate. Length about 0-003’ ; 
breadth in the middle 0-001’; at the shoulders 0:0012’. The specimen here 
figured is longer than usual, and the only one I have seen of this length. Margin 
punctate. There is a faint indication of a double keel in the middle of the valve. 
Striation fine, both transverse and oblique; strive about 48 in 0-001". 
This species occurs in several of the Loch Fine dredgings, and is not rare. 
The striation is similar to that of Tryblionella constricta, Grig. (Mic. Jour., vol. 
iii., pl. iv., fig. 13); but the present form is much larger, and is distinguished 
VOL. XXI. PART Iv. Tie 
