322 Proceedings of the Royal Irish Academy. 
sented without the median line, and having a longitudinal row of 
moniliform puncta interposed between the margin and the submar- 
ginal keels: the latter I have never been able to detect. Ralfs, in 
Pritch,, p...(Se,15 |. 1v,., ag. 30, Pl. ne. 140) and) hl) xt. mes. 
Grunow, Verhand. der K. K. Zool. Bot. Gesel., Band xii., 1862, p. 468. 
Heiberg, De Danske Diat., p.117. Rab. Fl. Eur., sect. 1, p. 148. 
Limestone quarry near Mullingar, Co. Westmeath. Marl-pit, Inch, 
near Gorey, Co. Wexford. Feighcullen, Co. Kildare. 
Amphipleura danica, (Kiitz.) Marine. 
Similar to the preceding in all respects, save that it is shorter and 
relatively broader. 
Kutz, Bac., p. 100, Toxxx., fie. oa... halls, in Prtch.. 0. dee 
Grunow, Verhand. der K.K. Zool. Bot. Gesel., Band xii., 1862, pp. 468 
and 470. Grunow is uncertain as to whether the median line has the 
elongated end nodules; but of this there is no doubt, my specimens 
invariably exhibiting the same: and he seems to regard the species as 
identical with Amphipleura rigida, Kiitz, this latter being in fact the 
same as Amphipleura sigmoidea, Wm. Sm., and belonging not to the 
genus Amphipleura, but to Nitzschia. 
Stomachs of Ascidians, Co. Clare. 
Famity VIII. NAVICULEA, Kiitz. 
Frustules oblong, having both valves furnished with a median line, 
central, and two terminal nodules. 
In this group I include all those forms with symmetrical frus- 
tules, more or less oblong elliptical in their outline, and haying 
both valves furnished with a median line, also with a central and two 
end nodules ; quite irrespective of their mode of growth, in tubes, stipi- 
tate, or free, filamentous or simple. So limited, Gomphonema, and 
Cocconeis, included by Heiberg as Naviculez cuneate, are necessarily 
excluded on account of the unsymmetrical structure of their valves ; 
while the species which normally occur, surrounded by a more or less 
amorphous mass of gelatinous investment, as Dickiea and Mastogloia, 
as well as those which grow in tubes more or less composite, as Ber- 
kleya, Colletonema, Schizonema; Doryphora, which is stipitate, Dia- 
desmis, which is filamentous, as well as the genera which grow free, 
and without any investment, are included, because their frustules, how- 
ever varying in minor details, ever exhibit the same general features. If 
Kiitzing, Smith and others, assigning too much value to the secondary 
modes of growth, have widely separated genera which are intimately 
related by a common structure, Heiberg on the other hand regards as 
