127 



the surface of the valves being only partially, instead of wholly 

 radiate, but the deltoid outline, truncate anterior end, and elevated 

 beaks are very characteristic features of all three genera and the 

 present species. 



In dealing with the mollusca of a comparatively new region, 

 and an almost unworked horizon, it is difficult to adopt many 

 known genera, on imperfect and incomplete materials, and it is 

 possible, therefore, tha,t A.? poststr-iaf a may represent an undescribed 

 and peculiarly Australian genus. 



When the shell is viewed looking at the anterior end, the latter 

 is seen to be flattened, or as I have described it above, straight- 

 walled, and the byssal opening to be large and somewhat cordate. 

 The form of this opening is quite in keeping with the structure of 

 Amhonycliia, an excellent tigure being given by Hall in his 

 " Supplementary note on the Genus Ambonychia,"* which exem- 

 plities it. The figured valve oi AJ: posf striata, the left one, is 

 three and three-quarter inches long, by three inches high, and with 

 a diagonal measurement of three and three-quarter inches. The 

 concentric sculpture of our species is similar to that of Amhonychia? 

 triton, Salter, f and so is the outline, but the posterior slope of the 

 latter is not radiate. 



Prof. Tate writes me that he possesses an Ambonychia-like shell 

 from Lilydale, with fenestrated ornament. It can hardly he A.? 

 poststriata, which is fenestrate only on the posterior slope. He 

 also informs me that the Rev. Mr. Cresswell gave him a small, 

 neat Conocardiwn from the same locality. 



Class GASTEROPODA. 



Order PROSOBRANCHIATA. 



Family Littorinid^^. 



fjeuns Cyclonevna, Hall, 1852. 

 (Pal. N. York, II., p. 89.) 



Cyclonema australis, Eth.Jil. 



(PI. xix., figs. 1 and 2.) 



C. ? australis, Eth. lil., Records Austr. Mus., 1890, I., pt. iii., p. 

 63, t. xix., f. 4 and 5. 



Obs. — I take this opportunity of figuring a far better specimen 

 of this species than I was formerly able to do. From it the 

 following characters are deduceable. The whorls are six in num- 

 ber, the body whorl being somewhat inflated. The spiral ridges 

 in this particular specimen are alternately larger and smaller, and 



* Pal. N. York, III., pt. i., p. 523, f. 2. 



t Mem. Geol. Survey Gt. Brit., II., pt. i., t. 23, f. 5. 



