492 PROFESSOR GREGORY ON 
C. dirupta, possibly the surface which lies under the one here figured, or possibly 
also the lower valve, which in Cocconeis is often different from the upper. It is, 
however, at least equally probable that these two forms belong to different species. 
In the Corallina gathering, C. dirupta is infinitely more frequent than C. diaphana. 
26. Cocconeis nitida,n. sp. Pl. TX., fig. 26. Form a very broad oval, suddenly 
contracted, above and below, to very short, subacute, produced apices. Length 
from 0:001” to 00038"; breadth from 0-0008” to 0:0035”. Valve very thick, 
aspect glassy. It is marked by lines of very large nitid granules, these lines 
forming, longitudinally, concentric strie, the two inner ones of which bend 
slightly outwards from the median line, leaving a narrow lanceolate blank space ; 
the others becoming more and more curved as they approach the margin. In large 
specimens, there are five such lines on each side, or from 3 to 4 in 0:001". But 
the granules also form transverse lines, much inclined near the apices, of which 
there are, in large specimens, 28 or 30 in the length of the valve, or from 6 to 8 
in 0001". The margin is marked by a series of finer striz. Median line obscure. 
In the middle of the valve, the transverse lines contain on each side five granules, 
corresponding to the five vertical lines. The granules are generally of equal size 
or nearly so, except a few near the apices, which are smaller. The whole form 
is very conspicuous, from its glassy aspect, and the size and brilliancy of the 
granules. 
This striking form occurs not unfrequently in Lamlash Bay, and sparingly in 
the Loch Fine dredgings. It is very uniform in its characters. 
27. Cocconeis pseudomarginata, n. sp. Pi. IX., fig. 27. Form a very broad 
elliptic, or elliptic-lanceolate. Length 0-0016” to 0:0033". Breadth 0-0011" to 
0-003". Valve thin and transparent. Within the margin is a line or shade parallel 
toit ; and within this, half-way from the margin to the centre, isa very strong line, 
forming a broad lanceolate figure. At first sight it seems as if the latter were the 
inner boundary of a marginal striated band; but on close inspection the striz, 
which are very fine, are seen to extend from the margin almost to the median 
line, where they leave a very narrow rhombic blank space, extending, in the 
median line, only to the inner of the two marginal lines. The third, or interior line, 
counting from the margin, is a very strong and raised ridge, the ends of which 
are almost in contact with the second line. Median line delicate, central nodule 
definite ; terminal nodules placed within the ends of the third line. Striz very 
delicate, but sharp, about 62 in 0-001”, transverse in the middle, nearly vertical at 
the ends. The first or outer margin is formed of two lines very close to each other. 
This remarkable form occurs in Professor Attman’s dredging from Lamlash 
Bay, where it is rather scarce, and also in that of Mr Mites from the same 
locality. It requires a very good glass to resolve the markings perfectly. 
28. Cocconeis major, n. sp. Pl. IX., fig. 28. Form avery broad oval. Length 
to 0:0015’ to 00038"; breadth from 0:001" to 000315”. Median line distinct ; 
