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. PI. IX., fig. 26. Form a very broad oval, suddenly 

 contracted, above and below, to very short, subacute, produced apices. Length 

 from 0-001" to 0-0038"; breadth from 0-0008" to 00035". Valve very thick, 

 aspect glassy. It is marked by lines of very large nitid granules, these lines 

 forming, longitudinally, concentric striae, 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 0-001". The margin is marked by a series of finer strise. 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 

 to it ; and within this, half-way from the margin to the centre, is a 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 striae, 

 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. Strise 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 Allman's dredging from Lamlash 

 Bay, where it is rather scarce, and also in that of Mr Miles from the same 

 locality. It requires a very good glass to resolve the markings perfectly. 



28. Cocconeis major, n. sp. PI. IX., fig. 28. Form a very broad oval. Length 

 to 0-0015" to 0-0038" ; breadth from 0-001" to 0-00315". Median line distinct ; 



