308 Proceedings of tlie Royal Society of Victoria. 



Ireland, by Professor Jones and to \vl)icli form tlie next variety 

 described is assigned. The present specimens, although agree- 

 ing with the former in thickness and edge view of the carapace, 

 are quite distinct, since X. wrightii has an ovate form of cara- 

 pace. 



The present specimens show considerable variation, but the 

 same general characters serve to connect them specifically. 



.Fig. 5, it should be noticed, is shown with the ventral side 

 uppermost, whilst in Fig. 8 it is turned downwards. In the 

 latter figure the posterior edge of the left valve is apparently 

 displaced beyond the edge of the opposing one. 



Locality and Horizon. — Cave Hill, Lilydale. Silurian (Yerin- 

 gian). 



Xestoleberis wrightii, Jones, var. oblonga, nov. (PI. XV., 



Figs, la, b). 



Observations. — The published figures^ of this species are not 

 nearly so elongate as our specimen, and since the latter is 

 longer and altogether larger than the already known forms of 

 the species it may be distinguished as a variety of X. wrightii. 



Locality and Horizon. — Cave Hill, Lilydale. Silurian (Yerin- 

 gian). 



Genus Aechviitta, Jones and Hall. 

 Aechmina jonesi, sp. nov. (PI. XIV., Figs. 11a, b). 



Description. — Carapace tumid, with a slightly concave ven- 

 tral, and strongly convex dorsal border ; ends unequally 

 rounded. Near the ventral border of each valve and towards 

 the posterior extremity there is a short, blunt and oblique 

 spine. Edge view subovate. 



Dimension's. — Length of carapace, .82 mm. ; height, to base 

 of spine, .57 mm. ; thickness, about .6 mm. 



Observations. — The above form seems to bear intermediate 

 characters between A. byrnesi Miller sp. Upper Ordovician)"-^ 

 and A. cuspidata Jones and Holl. (Silurian).^ 



1 Xestoleberis wrightii, Jones, 1890 : Qiiar. Journ. Geol. Soc, vol. xlvi., p. 28, pi. iv., 

 figs., 14, 15a-e. 



Xestoleberis (?) aff. wrightii, .Jones, Kraiise : Zeitschr. Deutsch. Geol. Gesellsch., 1891,. 

 p. 512, pi. xx.xiii., figs. 9a-c. 



2 Cincinn. Quar. Journ. Sei., vol. i., 1874, p. 123, fig. 10. 



3 Ann. Mag. Nat. Hist., ser. 4, vol. iii., p. 218, pi. xiv., fig. 8 and woodcut, fig. 2. 



