324 Froceedings of the Royal Physical Society. 



Fig. 9. Another specimen of the same, showing the mesial sinus and broad 

 concentric laminae of growth ; natural size. Parrot Creek. 



Figs, 10 and 11. A typical example of the same species, from the cliffs at 

 Wollongong, New South Wales, showing the characteristic concentric laminae 

 and three ribs on each side the shell ; natural size. Collector — Professor A. 

 Liversidge. 



Figs. 12-15. OrtJwtetes crenistria, var. senilis (Phillips), natural size ; 

 Havilah-Byerwin Pvoad, from a Marine Band in the Fresh-Water Series. Fig. 

 12. View of the dorsal valve and area of the ventral. Fig. 12a. Portion 

 of the surface magnified, showing punctse. Fig. 13. Ventral valve of the 

 same specimen, showing the conical form and gnarled appearance. Fig. 14. 

 Side view of the same specimen, both valves in apposition. Fig. 15. Side 

 view of another specimen. 



Figs. 16-18. Productus hrachythcerus (G. Sowerby), natural size. Fig. 16. 

 View of the ventral valve, with channels formed by the decurrent bases of 

 the spines. Fig. 18. Side view of the same specimen, showing the geniculated 

 form ; both from Stonelumpy Creek. Fig. 17. Dorsal valve, with the short 

 median septum a, and short hinge line hh ; Havilah-Byerwin Road, in a 

 Marine Band of the Fresh- Water Series, associated with OrtJwtetes crenistria. 



Figs. 18a.-25. Strophalosia Olarkei (Etheridge), natural size; various 

 localities. Figs. 18a, 19, and 20. Interiors of the dorsal valve ; Pelican and 

 Parrot Creeks. Figs. 21 and 22 the same. (= S. Woodsi. T. Davidson, 

 m. s.; Collection— 1l . Davidson, from New South Wales.) Figs. 23, 24, 25 

 the same. Pelican Creek. 



N.B. — The following letters refer to the same parts in the figures 18a-25 : 

 — CO, space left by the removal of the cardinal boss, septum, etc. ; h, bevelled 

 front margin ; c, lump of shelly matter showing thickness of valve ; d, rounded 

 alar angles ; c, cardinal boss ; /, sockets for teeth of the ventral valve ; g, elon- 

 gated septum ; A, h, oblique alar ridges ; i, i, depressions in which are situ- 

 ated the adductor muscles ; k, k, semilunar and narrow reniform impressions, 

 additional or front depression ; n, n, transverse septum between these depres- 

 sions. 



Figs. 26-32. Strojyhalosia Clarkei (Etheridge). Interior casts of the ventral 

 valve, natural size. Parrot Creek : — a, teeth ; b, ridge or se2)tum (groove in 

 casts) separating the adductor impressions ; c, ridges in the cast bounding the 

 latter ; d, blunt prominence (deep pit in casts) ; e, e, depression for cardinal 

 muscles, with grooves and ridges, forming scarp-like prominences in the cast ; 

 /, hinge spines; h, open channels left by spine bases; /, blunt umbo. 



Fig. 33. Strophalosia Clarkei (Eth.), with portion of the true shelly matter 

 adhering. Ventral valve natural size. Bowen River. 



Figs. 34-38. Strophalosia Gerardi, King? (See Perm. Foss. England, t. 

 19, f. 6 and 7). Natural size. Pelican Creek. Figs. 34 and 35, exterior of 

 the ventral valve, convex and round. Figs. 36 and 37, concave dorsal valve, 

 with the area and umbo of the ventral valve. Fig, 38, portion of surface of 

 another individual, showing spines — a, a, hinge line and area; b, concave 

 dorsal valve ; c, remains of spines on surface of yentral valve ; d, blunt but 

 not incurved umbo of ventral valve. 



Figs. 39-43. Strophalosia Jnkcsli, sp. nov. ? New South Wales and Tas- 



