NEW FORMS OF MARINE DIATOMACE. 49] 
sand. But in the former, a variety of C. Scutellum was figured by mistake: and 
the latter figure was imperfect, because I had not then seen the faint white bars. 
This species, along with C. costata, also figured in the third paper alluded to, is so 
frequent in Lamlash Bay, that I have had ample means of studying it, and am 
quite satisfied of its being a good species. I may say the same of C. costata, with 
the remark, that I cannot ascertain from EHRENBERG’s figures, whether his Ra- 
phoneis fasciolata may not be the same form. Enrenpere’s form seems to be 
much larger, and the markings much coarser and more conspicuous. I must 
leave this point undecided till I can compare the two forms. 
24. Cocconeis ornata, n. sp. Pl. 1X., fig. 24. Form a pure and elegant oval. 
Length about 0-0022"; breadth about 00014”. There is a broad marginal band, 
marked by strong distant coste, the ends of which are rounded. Within this 
band the surface appears concave to the median line, which is delicate, with a 
large, definite, central nodule. The middle part is marked by fainter costze, cor- 
responding to those on the marginal band, and, like them, so much inclined near the 
apices, as to be nearly vertical. There is a narrow blank line between the marginal 
and central costz, and the latter do not reach the median line, leaving a long lan- 
ceolate blank space in the middle. The whole valve has a rich ornate aspect. 
This beautiful species occurs in Lamlash Bay; and although scarce as yet, I 
have been able to examine a sufficient number of specimens to ascertain its cha- 
racters. I have also observed a few in Loch Fine. 
25. Cocconeis dirupta, n. sp. Pl. IX., fig. 25. Forma broad, short oval, some- 
times all but orbicular. Length from 0-001” to 0:0024” ; breadth from 0:0007” to 
_ 00021". Valve thick, and under the half-inch objective of a strong brown colour. 
Median line irregular, like a slit or tear down the middle of the external surface. 
The whole valve is marked, except the slit, with coarse, wavy, longitudinal striz ; 
but, when carefully focussed, fine transverse strize are seen over the whole surface 
to the median line. Under the half-inch, there is an appearance of a long stauros, 
which, under a higher power, disappears as such, and can only be seen as a trans- 
verse gleam of light from below. The striated surface seems to be an outer one, 
torn asunder in the middle, and from this I have named it. Vertical strize about 
26, transverse strize about 60 in 0-001”. 
I had observed this form in the Glenshira sand, where, however, it was very 
scarce, and hardly ever entire, so that I postponed its investigation. It occurs 
very abundantly in Mr Mixes’s Corallina gathering, and less frequently in several 
of the dredgings. There is but one known form which is in any degree allied to 
it. This is C. diaphana, Sm., which I find to occur along with it. After many 
comparisons, I am disposed to conclude, although these two forms are not the 
same thing, since C. dirupta is by no means diaphanous, while its strice are con- 
spicuous and its colour brown, the strize of C. diaphana being very obscure, and 
the valve colourless, that C. diaphana may perhaps be an imperfect form of 
