14 
iioithei* extend laterally as far as the posterior lateral margins of the valves 
nor terminate in an extended point or mucro. The costse are very numerous 
hut variable in number, and both primary and secondary, the latter interpolated. 
In all, the costm vary from thirty-five to fifty; the anterior auricles are radiate, 
and the posterior apparently plain. The hinge-jdate is quite linear, with 
delicate resilium furrows. 
AVe have not observed frill-like decussations in any of our New South 
Alcaics exam})les, hut they were ([uite apparent in those from AA^cstcrn Australia 
examined by one of us. AA^e have not seen specimens of the right valve. 
Localities (Did Iloidzou. — llavenstleld [J. Waterhouse, T. W. 
Edgeu;orth David)-, Farley (J. Waterhouse). — Permo-Carboniferous— Lower 
Marine Series. 
Collection^ — Alining and Geological ATuseum. 
Aviculoi’ecten, sg. 
(Plate XV, Figs. 11 and 12.) 
Ohsercations . — Amongst the Carboniferous Pala'opcctens recorded by 
l)e Koitinck is one referred to Pecten knockonniensis, AlcCoy,^ of the Irish 
Carboniferous Limestone. No satisfactory evidence of the ('xistence of this 
species in Austmlian rocks has come under notice, but we possess three 
specimens which may be that described by De Koninck as Avicidopecten 
knockonniensis,- but as the d(‘scription is unaccompanied by a figure, and 
appeal’s to be taken from nearly perfect exotic material, rather than specimens 
in the usual imperfect state of our New South AAalcs fossils, we are completely 
left in the dark as to the nature of those recorded in the Clarke Collection 
under this name. 
AAA believe the best preserved of our three specimens to be a left 
valve, and if this be so, then they are most assuredly not AlcCoy’s species. 
The valve in question is elongately orbicular, with a large number of fine, 
equal costm similar to those of the left valve of P. knockonniensis, AIcCoy, 
and in addition cvim finer concentric lines crossing them. This, however, is 
’ McC.'oy — Synop. Carb. Lime. Foss. Ireland, 1844, p. 95, t. 17, f- 4. 
^ l)e Koninck — Kech. Foss. Pal. Xouv.-Galles ilu Slid, Pt. 8, 1877, p. 150. 
