116 O’MEARA, ON DIATOMACEA. 
longitudinal band close to the median line; the interspaces 
blank. Properly this form belongs to the Pinnularie ; but 
although the reasons assigned for merging the latter family 
in the Navicule seem scarcely satisfactory, I feel disposed to 
fall in with the tendency in this direction when the form 
presents the general characteristics of the Navicule. This 
species bears a striking resemblance to Navicula Egyptiaca, 
described by the late lamented Dr. Greville in the last 
number of the ‘ Microscopical Journal.’ Navicula denticulata, 
however, is distinguished from that just referred to by the 
following characters:—It is much shorter and broader, the 
marginal striz are longer, the central striz are nearer to the 
median line, and continuous instead of being interrupted 
towards the central nodule as in the case of Navicula 
Egyptiaca. 
Navicula Wrightti, nu. sp., O’M., fig. 4—Valves broadly 
elliptical ; length 0041, breadth -0024; striee fine, marginal ; 
there is a broad band at either side of the median line, linear, 
interrupted towards the central nodule, shghtly constricted as 
it approaches the marginal band of strie, and then expand- 
ing towards the apex, which is mammiform. ‘This longitu- 
dinal band is destitute of strie. On first inspection this form 
is hable to be mistaken for Navicula Hennedyi, but it is soon 
distinguished from it, not only by its mammiform apices and 
the spathulate extremities of the longitudinal median band, 
but also by the fact that in the present species this band is 
blank, while in Navicula Hennedyi it is striate. A variety of 
this species is described in fig. 4 8, much smaller than the 
other, and having the sides nearly parallel. Length -0030, 
breadth ‘0014. 
Navicula amphoroides, n. sp., O’M., fig. 5—Valve ellip- 
tical, narrow; length :0032, aaa 0014. In this form 
the central nodule is depressed, and the median line waved ; 
strie moniliform, in the middle approaching the central 
nodule, and becoming gradually shorter towards the ex- 
tremities. 
Pinnularia Arraniensis, n. sp.,O’M., fig. 6.—Valve broadly 
elliptical; length ‘0030, breadth -0017; striz coarse, dis- 
tinctly costate, not reaching the median line. In some 
aspects this form resembles Navicula Smithii and Navicula 
estiva, Donk., but differs from the former by its distinctly 
costate striae, and from the latter by the coarseness of its 
striz, as also by the fact that it is much broader in propor- 
tion to its length than NV. estiva. 
Pinnularia divaricata, n. sp., O’M., fig. 7.—Broadly ellip- 
tical, costate ; length ‘0058, breadth 0035; the ends slightly 
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