145 
abundant in Carboniferous rocks that a detailed description of it here seems 
superfluous. As I have before stated this species is easily recognized by the 
gibbosity of its ventral valve, and by the concentric folds covering the ears 
and visceral region of the same valve, crossing at right angles to the longi- 
tudinal rihs of the surface, and thus producing a reticulated design very rarely 
so pronounced in any other species. The dorsal valve is nearly fiat in the 
visceral region, and is recurved at nearly a right angle so as to produce a 
prolongation which applies itself directly to that of the ventral valve and 
follows all its curves. This sjiecies is rather subject to considerable variation 
in size ; sometimes its prolongations are very short and do not exceed one 
centimetre in length, while sometimes they reach a length of from seven to 
eight centimetres, without any modification of the principal part of the shell. 
Often its longitudinal ribs are smooth or slightly tuberculous ; while the 
surface of some specimens bristles with tubular spines, some as much as six 
or seven centimetres long. The Australian specimens are of medium size 
and approach the variety which J. Phillips has figured under the name of P. 
pugilis. 
Horizon and Localities. — This sj)ecies, which is one of the most 
abundant, the most widespead, and the most characteristic in the Carboniferous 
rocks of Europe, is rather rare in Australia, in spite of the great development 
of these rocks there. Eive well preserved specimens, all like those from the 
Belgian Carboniferous rocks, were sent me by the Bev. W. B. Clarke, who 
found them in a greyish or brownish limestone at Glen William and Colocolo. 
A sixth comes from the banks of the Williams River, where it was found in 
a grey, argillaceous limestone, associated with several other species. 
Productus undattjs, Lefrance} 
PL IX, Fig. 4.1 
Lroductus undatus, Defrance, 1826, Diet. Sc. Nat., XLIII, p. 354. 
,, 5, L. Gr. de Koninck, 1842, Descr. Anim. Foss. Terr. Carb. Belg., p. 156, 
pi. 12, fig. 2. 
„ tortilis ? McCoy, 1844, Synop. Carb. Foss. Ireland, p. 116, pi. 20, fig. 14. 
,, undatus, de Verneuil, 1845, Eussia and Ural Mts., II, p. 261, pi. 15, fig. 15. 
,, ,, L. Gr. de Koninck, 1847, Eecb. Anim. Foss., I, p. 59. pi. 5, fig. 3. 
'■ [PI. XI, fig. 4. Vide Etheridge, R. Jimr., Geol. and Pal. Q’land, 1892, p. 254, pi. 12, fig. 16. — W.S.D.] 
