O’MEARA, ON NEW FORMS OF DIATOMACE2. 247 
coste filled up by three lines of puncte, the two outer lines 
reaching the central vacant space or rhaphe, the intermediate 
line much shorter. ‘This species, in its general characters, 
very much resembles a form figured by Grunow, and with 
hesitation regarded by him as a variety of Cocconets Grevillit. 
The absence of a median line and central nodule, as well as 
the presence of a distinct raphe, mark the present form as 
belonging to the genus Rhaphoneis. The form figured by 
Grunow is narrow elliptical ; mine is nearly orbicular. These 
differences notwithstanding, I am disposed to think that 
Grunow’s form and mine are at most but varieties of the 
same species. 
Rhaphoneis Jonesii, n. sp., O'M., fig. 10, x 600.—Valve 
broadly elliptical ; length -0018, breadth -0014. Striz radiate, 
moniliform; cellules close, compressed, very large at the 
margin, and gradually decreasing in size towards the raphe, 
which is narrow and elliptical. 
Rhaphoneis Moorii, n. sp., O’M., fig. 11, x ‘600.—Valve 
broadly elliptical ; length ‘0016, breadth ‘0011. Striz radiate 
moniliform cellules of the same size throughout, raphe 
narrow. At first inspection of the figures it might appear 
that this form is identical with the preceding, but on con- 
sideration the differences are so great as to warrant me in 
regarding them as distinct species. The raphe in the 
former, though narrow, is wider than in the present. The 
former has a distinct border, this has none; but the most 
marked difference is to be found in the character of the 
strie ; in the case of R. Moorii the cellules which form the 
striz are all of nearly the same size, round, and distant ; 
whereas in the case of R. Jonesii the cellules are so close as 
to give a costate appearance to the strie; they are also 
flattened, and decrease in size from the margin towards the 
raphe. 
Rhaphoneis Archeri, nu. sp., O’M., fig. 12, x 600.—Valve 
elliptical. Strize slightly radiate, distinctly costate, distant ; 
raphe lanceolate. A form described by Grunow, and 
by him called Rhaphoneis scutelloides, so far as the figure is 
concerned, so closely resembles the present that at first [ 
was disposed to regard mine as identical with it, but from 
the description there is no doubt it is distinct. The strie of 
R. scutelloides are described by Grunow as “ indistincté 
puncte ;” in R. Archeri they are distinctly costate. 
