172 
by a fold, the side of which furthest from the furrow is strongly developed, 
and reaches the bottom of a second lateral fold a little recurved, and much 
less angular than the first lateral fold. The beak is much more acute than 
that of the ventral valve, beneath which it articulates ; the lateral parts of 
the beak are depressed. The external surface of the shell is provided with a 
number of nearly equidistant concentric lines of growth. 
Dimensions. — The length is tliirty, the breadth twenty, and the thick- 
ness fourteen millimetres. 
Relations and Differences. — This species strongly resembles the 
variety R. angulata, Linne, which Mr. Davidson represented in PL 19, Pig. 
13 of his Monograph of the Carboniferous Brachiopods of the British 
Islands. The mesial fold, instead of being on the dorsal valve, as in most 
Rhynclionellce, is on the ventral valve, occupying its whole length, and being 
replaced on the dorsal valve by a corresponding furrow. But it is possible to 
distinguish between the two, because in R. inner sa the ribs and the front 
are sharply cut, while they are obtuse in every variety of R. angulata, as 
Mr. Davidson’s numerous figures of it prove. Again, I have examined many 
specimens of R. angulata, and have never noticed any lines of growth on its 
surface like those of R. inversa. Besides, the beak of R. inversa is much 
thicker, and its foramen much larger and more oblique. 
Horizon and Localities. — A single specimen of this beautiful species 
was found by the Bev. W. B. Clarke in the Muree Quarry, Baymond Terrace, 
near the junction of the Williams and Hunter Bivers. 
Genus — ATHYBIS, McCoy. 
Athteis planosulcata, J. Rhillips.^ 
PL XT, Pig. 6.- 
Spirif era planosulcata, J. Phillips, 1836, Geol. Yorkshire, II, p. 220, pi. 10, fig. 15. 
Terebratula de Royssii, E. de Yemeuil, 1840, Bull. Soc. Geol. Prance, XI, p. 259, pi. 3, 
L fig. la and Ic (fig. Ih, Id, le exclusis, non Leveille). 
Atrypa planosulcata, J. de C. Sowerhy, 1840, Min. Conch., VII, p. 15, pi. 617, fig. 3. 
,, ohlonga. Idem, 1840, ihid., p. 16, pi. 617, fig. 3. 
* \Actinoco 7 icJms 2 }^cinosidcatus. — R. Etheridge, Junr., Records Geol. Survey N. S. Wales, 1898, v, Pt. 4, 
p. 177, t. 19, f. 18. Athijris Fioysii, R. Etheridge, Junr., Procs. Linn. Soc. N. S. Wales, 1895, IX, Ft. 3, p, 529, 
t. 39, f. 4.— W.S.D.] 
2 [PL IX, fig. 6.— W.S.D.] 
