Victorian Fossils, Fart XVI. J05 



ridge depressed and concave towards the cardinal extremity. Hinge 

 line straight, extremities acute and more or less extended; anterior 

 margin regularly and bioadly rounded. Brachial valve concave, 

 with two divergent folds or flexures of the shell-surface. Surface 

 of both valves punctate, bearing about 30 thin radial riblets with 

 fine intermediate striae near the anterior border. 



Measurements. — Pedicle valve (Cotype) : Length, .'5.5 iniii. ; widtli. 

 5.25 mm. Another example (Paratype) : Length, 4.5 nuii. ; width. 

 8 mm. Brachial valve (Cotype) : Length, 3.25 mm. ; width, 5.5 mm. 



Observations. — This neat little species belongs to the section of 

 the genus styled Plicosae, having not more than 30 riblets. It 

 agrees to some extent with the Wenlock species, Chonetes minima, 

 Sowerby sp.,i but differs to a marked extent in the median division of 

 the umbonal ridge, and by having a generally Avider or more 

 transverse shell. The " Leptaena " winiina referred to by Prof. 

 McCoy on quarter sheet No. 4 S.W. locality Bb 20. Kilmore Cieek. 

 probably related to this or an allied species. 



Occurrence. — Silurian (Yeringian). Common in the nmdstone of 

 Ruddock's Quarry, near Lilydale; and at the Geol. Surv. locality 

 Bb 16, at Simmonds' Bridge Hut on the Yarra. 



Fam. Pentameuidae. 



Genus Conchidium, Linne. 



Conchidium kniyhtii, J. de C. Sowerhy, .sp. Plate XI., tig. 11. 



Pentamerus knightii, Sowerby, 1813, Min. Conch., vol. i., p. 7.3. 

 pi. xxviii. Idem, 1839, in Murchison's Silurian System, p. 615. 

 pi. vi., figs. Sa-c. Davidson, 18GT, Mon. Sil. Brach. (Pal. Soc). 

 vol. XX., p. 142, pi. xvi., figs. 1-3; pi. xvii., figs. 1-10; pi. xix., fig. 

 .3. Etheridge, R., jnr., 1892, Rec. Geol. Surv., N.S.Wales, vol. iii.. 

 pt. 2, p. 54. pi. X., figs. 1-6; pi. xi.. figs. 1-4. 



Observations. — This fossil is not uncommon in the Silurian sand- 

 stones of Heathcote, Victoria. The examples are mostly in tlu' 

 condition of internal casts of the shell, but where the outer sIr-II 

 ornament is preserved the characteristic costatiou is seen. 



Mr. Etheridge records this species from various localities in New 

 South Wales, in strata of Silurian age, which he calls the " Peur 

 tamerus Limestones," and remarks on the fact of its being a 

 characteristic fossil of the Aymestry Limestone in Wales and the 

 W^est of England, occurring sparingly in the underlying Weiiloek 

 and the overlying Upper Ludlow. 



1 Leptaena ininhna, Sowertiy, in Murchison's Silurian System, 1S39, pi. xiii., figs. 4, 4a. 



