322 Proceedings of the Royal Irish Acadennj. 



sented withoiit the median line, and having a longitudinal row of 

 monilifoiTa puncta interposed bet^veen the margin and the submar- 

 ginal keels : the latter I have never been able to detect. Ralf s, in 

 Pritch., p. 783, PI. iv., fig. 30, PI. ix., fig. 140, and PI. xiii., fig. 1. 

 Gmnow, Verhand. der K. K. Zool. Bot. Gesel., Bandxii., 1862, p. 468. 

 Heiberg, De Danske Diat., p. 117. Eab. Fl. Eur., sect. 1, p. 143. 



Limestone quarry near Mullingar, Co. "S^^estmeath. Marl-pit, Inch, 

 near Gorey, Co. Wexford. Peighcullen, Co. Kildare. 



Amphipleura danica, (Kiitz.) Marine. 



Similar to the preceding in all respects, save that it is shorter and 

 relatively broader. 



Kiitz. Bac, p. 103, T. xxx., fig. 38. Ealfs, in Pritch., p. 783. 

 GrunoTv, Yerhand. der K.K. Zool. Bot. Gesel., Band xii., 1862, pp. 468 

 and 470. Grunow is uncertain as to Tvhether 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 ^vith Amphipleura rigida, Kiitz, this latter being in fact the 

 same as Amphipleura sigmoidea, "Wm. Sm., and belonging not to the 

 genus Ampliipleura, but to Mtzschia. 



Stomachs of Ascidians, Co. Clare. 



FAinxT YIII. yAYICIILE..E, Kutz. 



Prustules oblong, having both valves fui-nished with a median lino, 

 central, and two terminal nodules. 



In this gi'oup I include all those forms with symmetrical frus- 

 tules, more or less oblong elliptical in their outline, and having 

 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 oS^aviculeaB cuneatae, are necessarily 

 excluded on account of the unsymmetrical structure of their valves ; 

 while the species which normally occiu', surrounded by a more or less 

 amorphous mass of gelatinous investment, as Dickiea and Mastogioia, 

 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 frustiiles, 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 



