NEW FORMS OF MARINE DIATOMACEZ. 507 
of the valve, in a narrow, elongated nodule, which is in a line with the terminal 
nodules, also long and narrow. But close to the outer margin, at the constric- 
tion, is another large round nodule. The narrow portions, which lie between 
the curve-lines just mentioned and the inner margin of the valve, appear, like 
the middle space, to be unstriated ; but perhaps this is because they lie in a 
different plane from the outer compartments. And even in the last, the strize are 
too fine to be resolved under a power of 400. 
This remarkable form occurs in one of the Loch Fine dredgings, where, how- 
ever, it is very scarce. I have not yet recognised with certainty the S.V., but 
there are some forms which may prove to belong to it. 
61. Amphiprora maxima, n. sp. Plate XIL., figs. 6land 610. Form of F.V. 
rectangular, very broad, but deeply constricted in the middle, and rounded on the 
ends. Length 0°0068"; greatest breadth 0:0028" to 0:003", breadth of frustule at 
constriction 0:0017’. Central nodules large, situated close to the constriction in 
the outer margin. Terminal nodules on the inner margin of valves, conspicuous. 
Over each valve lies a strong, broad plate, arcuate outwards, straight on its inner 
margin, which coincides with that of the valve. Outer margin of plate prominent 
in the middle, and on each side of this prominence slightly incurved; thick, over- 
lapping the valve at the constriction. Breadth from the margin of one plate at 
this point to that of the other 0:0023’. Valves and. plates transversely striated. 
Strize distinct, parallel, about 36 in 0-001’, thicker and apparently coarser at the 
margin of the plate. S.V. lanceolate, ends acute, with a trace of a constriction just 
before the apices. Greatest breadth 0:00125". Two strong lines, as in Apr. lepi- 
doptera, proceed from the apices, on one side, and curve inwards to join a large 
nodule at one-third of the width. Round this nodule the strice are curved, as if 
pushed outwards. Between the nodule and the nearest margin the strize are very 
short, and they leave a large blank space, extending tothe margin. Valve thick and 
very convex on the S8.V. Query, Are the curve-lines on the S.V.. the outer margin 
of the plates, seen on the F.V? From the convexity of the S.V. its striation is more 
conspicuous than that of the F.V. 
_ This, which is one of the finest and most interesting forms described in this 
paper, first attracted my attention in the Glenshira Sand. But I could only find 
there halves of the F.V; and I postponed the description of it. In Professor ALL- 
MAN'S Lamlash Bay dredging I again saw these halves occasionally ; but it was 
not till I examined, in October last, the Loch Fine dredgings, that I found, in one 
of them, besides a number of the same halves, some entire frustules ; and finally, 
the S.V. which, from its comparative narrowness, is seldom presented; the frus- 
tule or detached valve lying on its broadest side. There is something very beauti- 
ful in the entire form; and in its structure it is peculiarly interesting, as present- 
ing the peculiar lateral plates, already noticed in Apr. pusilla, Apr. plicata, and 
Apr. lepidoptera, and that ina high degree of development. The occurrence of 
