66 Proceedings of the Royal Society of Victoria. 



gently towards the anterior border. The edges of the lateral 

 shoulders nearly straight and meeting the boldly curving anterior 

 margin at less than halfway from the umbo. Shell thin and 

 wrinkled externally, boldly relieved by deep curved lines of 

 growth, about 10 or 12, from their salient edges proceed numer- 

 ous spines, of which only vestiges remain. There are also 

 indications of surface pittings between the bases of the spines. 

 Pedicle opening small, circular, and with a depression indicating 

 the position of the underlying pedicle tube which pi'oceeds from 

 it anteriorly (Fig. 8). Dorsal valve smaller, depi'essed-couvex, and 

 sub-circular in form. The internal cast of the pedicle valve 

 shows the position of the foramen at the summit of the valve, 

 and a deep groove, the impression of the tul»ular canal. 



Measurements. 



Length of a pedicle valve - - - - 14 mm. 



Width of a pedicle valve - - - - 12.5 „ 



Length of a brachial valve- - - - 11 ,, 



Width of a brachial valve - - - - 9.5 ,, 



Length of a large brachial valve (figured) - 14 „ 



Width of a large brachial valve (figured) - 14.5 ,, 



Affinities. — In some respects S. australis seems related to S. 

 anglica, Morris\ as for example in its relatively large size, the 

 prominent lines of growth, and the pitted shell-surface. Our 

 specimens differ in certain points which render them specifically 

 distinct ; it is generally much larger than S. anglica, and it is nob 

 so deeply nor so numerously pitted as that species. 



Occurrence. — Found in the hard black argillaceous rock, 

 Domain Road, South Yarra (Sewerage Works), [903-609]. Also 

 as casts, in brown micaceous sandstone, Swanston Street Sewer 

 [600-1], and from the Sewerage Tunnel near Old Fish Market, 

 Flinders Street [610-11]. Collected by Mr. F. Spry. 



Horizon. — Silurian (Melbournian). 



Genus Orlnculoidea, d'Orbigny. 



Orbiculoidea selwyni, sp. nov. (PI. X. Figs. 5, 6, 6a, 12). 



Specific characters. — Pedicle valve broadly elliptical. Apex 

 excentric, situated at less than one fourth the length of tlie shell 



1 Ann. Nat. HiRt., 2nd ser., 1849, vol. iv,, p. 320, pi. vii., flgs. lae. 



