490 PROFESSOR GREGORY ON 



GROUP II. 



COCCONEIDES. 



The new forms belonging to this group are not numerous, but they are, in 

 every case, interesting. In addition to one species, already figured, though im- 

 perfectly, as occurring in the Glenshira sand, I have detected in the new materials 

 six additional species, all of them beautiful and well-marked forms. These con- 

 stitute a largeaddition to a genus, which, in Britain at least, has hitherto been a 

 very small one. The species to be described are : — 



23. Cocconeis distans, Greg. 



24. ... ornata, n. sp. 



25. ... dirupta, n. sp. G. 



26. ... nitida, n. sp. 



27. Cocconeis pseudomarginata, n. sp. 



28. ... major, n. sp. 



29. ... splendida, n. sp. 



23. Cocconeis distans, Greg. PL IX., fig. 23. Form oval, broad ; ends subacute. 

 Length from 0-0014" to 0-0026" ; breadth from 0-001" to 0-002". Median line 

 delicate. The valve is marked by distant lines, much inclined near the apices, 

 not reaching the median line. These lines are about 10 in 0001", and consist of 

 white hyaline faint bars, on which are set small and distant granules. The 

 number of granules is only 4 or 5 in the longest of these lines, so that the gra- 

 nules are very distant. They are, as nearly as possible, of equal size, and from 

 their distance, give to the valve a spotted rather than a striated aspect. In the 

 figure, the granules appear larger than they really are ; but this, as I have since 

 ascertained, depends on the focus, and is an effect of shadow. By careful 

 focussing, the real size of the granules is easily seen. The valve is hyaline ; but 

 it is always easy, by focussing, to see the faint bars on which the granules are set, 

 a character which at once distinguishes this form from C. Scutellum, to which 

 some are disposed to refer it. Another character, besides that of its having much 

 fewer lines and much fewer granules than the coarsest varieties of C. Scutellum, 

 is, that in C. distans the granules are of equal size, while in C. Scutellum they 

 diminish in size as they approach the median line. In C. distans, if there be any 

 difference, it is that the marginal granules are somewhat smaller than the others. 

 I may here also allude to the fact, that while C. Scutellum is a most variable form, 

 C. distans, so far as I have seen, exhibits only one variety, and that quite dif- 

 ferent from any variety of C. Scutellum. This form, C. distans, var. j3, jwoemorsa, 

 is considerably larger than the type, having a length of 0-003" to 0-0038", and 

 being a little narrower in proportion than the type. There is always, at one 

 point of the margin, a notch or solution of continuity, as if a portion had been cut 

 out, and then smoothed over. The only other difference is, that the granules 

 are somewhat smaller, but the faint bars are exactly as in the type. 



I figured this species, both in my first and in my third paper on the Glenshira 



