183 
ventral valve is rather regularly curved; its heak is thick hut not very 
prominent ; its ears rounded ; its hinge area triangular, rather raised, and 
curved ; and its deltoid fissure triangular, and broad at the base. The rather 
deep ventral furrow is divided in the middle by a well-marked fold, though 
usually less well-marked than the five or six lateral folds. The dorsal valve 
is rather more ventricose than the ventral valve ; its dorsal ridge is divided 
centrally by a furrow corresponding to the fold of the ventral furrow. The 
lateral folds number five or six, are slightly curved, and diminish in thickness 
as they recede from the centre of the valve. The cardinal process is like that 
of most Spirifers, hut the muscular impressions are small, faint, and super- 
ficial. 
Dimensions. — One of the Australian specimens is about four centi- 
metres long and five centimetres broad. 
Relations and Differences. — This species differs from 8. omformis 
and 8. Darioinii by the mesial fold dividing the ventral furrow, no trace of 
such fold being visible in either of the species just mentioned. 
horizon and Localities. — Mr. McCoy says that this 8pirifer is not 
uncommon in the limestone of Wollongong, and the sandstone of Muree 
Quarry. Mr. J. I). Dana found it in the Illawarra District ; and Mr. W. B. 
Clarke at Wollongong, Bomhaderra Creek, at Stroud, and at fiEllalong. 
Spirifer strzeleckii, L. Q. de Koninch} 
PL XIII, Pig. 1 and PL XIV, Fig. 1. 
8pirifeTa undifera, var. undulata, E. Etheridge, Senior, 1872, Quart. Journ. Greol. Soc., 
XXVIII, p. 330, pL IG, fig. 3-5 (non F. Eoemer). 
This is a transverse, subrhomhoidal shell, with valves of nearly equal 
depth, having its greatest transverse diameter towards the middle of its length. 
The ventral valve is regularly curved, and has a broad deep furrow rounded 
at the bottom. By the sides of the ventral furrow are four rather thick 
folds, — this number includes the folds bounding the ventral furrow. These 
folds are rounded and divided from each other by furrows of the same breadth 
as the folds . The heak is thick hut not prominent ; the hinge area is very 
much elevated, and is nearly as long as the shell is broad, it is very slightly 
1 [Vide R. Etheridge, Junr., Geol. and Pal. Q’land, 1892, p. 234, t. 10, f. 5-7.— W.S.D.] 
