NEW FORMS OF MARINE DIATOMACES. 489 
rently marginal, strong, about 20 in 0-001”, giving the appearance of a narrow 
marginal band of very strong costee. Within this band, however, the valve, on 
close inspection, is found to be marked with similar but much fainter coste 
nearly to the median line. The valve appears to be thicker near the margin than 
in the middle, and this perhaps is the reason why the coste are so strong and 
conspicuous there. 
This form is frequent in Professor ALtman’s dredging from Lamlash Bay, and 
it occurs also in Loch Fine. I have named it after Professor ALLMAN, to whom I 
am indebted for this dredging, the richest of all those here described. 
22. Pinnularia Pandura= Navicula Pandura, Bréb., var. 8, elongata. PI. IX., 
fig. 22. Form deeply constricted in the middle, with elongated sub-triangular 
ends, and obtuse apices. Length 0-0075” or more; greatest breadth 0-002”, breadth 
at constriction 0-0014”. Median line sharply defined, broader at the centre than 
at the ends; nodule square, definite. On each side of the median line, and a 
little way from it, there is on each side a line or ridge, apparently formed of large 
granules, but probably only apparently so, from the sudden and sharp elevation 
of the ends of the costae. Coste, from this point to the margin, perfectly entire 
and glassy, like those of P. alpina. Valve thick, costz 10 or 11 in 0-001”, some- 
what inclined near the apices. 
This seems to be a variety of Dr Brepisson’s Navicula Pandura, which I have 
represented in the second paper on the Glenshira sand, in figs. 11, 12, and 12*. 
But as De Bresisson himself describes the coste as being entire, and represents 
them distinctly so in his figure of the species, I have changed the generic name to 
Pinnularia. 1 consider it as quite distinct from WV. Crabro, Ehr., as described by 
Professor Smiru, in vol. ii., of the Synopsis; for the latter has obscurely monili- 
form strize, as is shown in Dr Grevitix’s figure of it from Trinidad, in the Micro- 
_ scopical Journal for January 1857. 
The forms represented in figs. 11, 12, and 12* of my second paper on Glenshira 
(Mier. Trans. iv., pl. v.), and that here figured (fig. 22), are abundant in several 
_ of the dredgings; but of all the numerous examples I have examined, not one 
exhibits the slightest trace of moniliform structure; and I have had the satisfac- 
_ tion of having this observation confirmed by Dr Greviize, who is acquainted with 
_ the form in which that structure exists obscurely. Unless, therefore, we are pre- 
_ pared to abolish the distinction between entire and moniliform striation, on which 
_ Professor Smit founds the distinction between his genera Navicula and Pinnu- 
-laria, we cannot regard this form as a Navicula. 
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VOL. XXI. PART Iv. 6Q 
