306 Proceedings, of tlie Royal Society of Victoria. 



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

 gian). 



Primitia semicircularis, Jones and Holl. (PI. XV., 

 Figs. 4a-c). 



Primitia semicircularis, Jones and Holl, 1865. Ann. Mag. 

 Nat. Hist., ser. 3, vol. xvi., p. 424, pi. xiii., figs. 10, a/-c. 



Observations. — The specimen figured by Jones and Holl from 

 the Silurian drifted limestone of N. Germany almost exactly 

 matches our specimen, but the latter is not quite so acutely 

 produced anteriorly. 



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

 gian). 



Ppimitia unicopnis, Uhich sp. (PL XV., Figs. 6a, b). 



Leperditia unicornis, Ulrich, 1879. Journ. Cincinn. Nat. Hist. 

 Soc, vol. ii., p. 10, pi. vii., fig. 4. 



Primitia unicornis, Ulrich sp., Jones, 1890. Quart. Journ. 

 Geol. Soc, vol. xlvi., p. 7, pi. iv., figs. 8-13. 



Observations. — This species shows a large amount of varia- 

 tion in its general shape, being typically faboid, with a shallow 

 dorsal depression and a posterior tubercle usually situated near 

 the ventral angle, but in our specimen .seen near the middle of the 

 poisterior border. P. unicornis has hitherto been recorded only 

 from the Upper Ordovician of Wales and the United States. 



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

 gian). 



Family Cytheridae. 



Genus Xestoleheris, G. O. Sars. 



Xestoleberis holliana, sp. nov. (PL XIII., Figs. 3a-c). 



Description.— Carapace elongate ovoid. Seen from the side 

 elongate or subrectangular, dorsal margin slightly convex, 

 rounded at the ends ; anterior margin meeting the ventral 

 border bluntly, and forming a slightly salient angle ; the pos- 



