302 Proceedings of the Royal Society of Victoria. 



concave in the centre ; extremities of carapace compressed, the 

 edges of the valves forming a flange-like border which, ante- 

 riorly, is somewhat produced and sloped gently away to the 

 dorsal and ventral edges; whilst posteriorly the dorsal angle is 

 evenly rounded, and the ventral rather irregularly so, making a 

 wider angle with the ventral border. Edge view sub-triangular, 

 broad posteriorly, and gradually sloping away towards the 

 anterior end, ^\^th a depressed area, however, in the region of 

 the dorsal sulcus ; thickest in the middle of the posterior third. 

 End view sub-elliptical, rather compressed ventrally, rounded 

 dorsally. Surface of valves finely punctate ; with a narrow but 

 distinct median channel, at right angles to the dorsal edge, end- 

 ing in a small pit-like depression near the centre of each valve. 



Dimensions. — Length of carapace, .85 mm. ; height, .3 mm. ; 

 thickness, 5 mm. 



Observations. — The above species seems to present us with a 

 somewhat exceptional type of Primitia in the striking character 

 of the flange-like extremities. A comparison of the species 

 which come nearest to this form leads one to see a probable 

 ally in Primitia renulina, Jones and Holl,^ from the Wen- 

 lock Limestone of Malvern, England. The latter species is, 

 however, markedly distinct from ours in having a sub-oval valve, 

 and a saddle-shaped depression close to the dorsal margin. 



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

 ingian). 



Primitia (?) matutina, Jones and Holl. (PI. XTII., 

 Figs. 5a, b). 



Primitia ? matutina, Jones and Holl, 1865. Ann. Mag. Nat. 

 Hist., ser. 3, vol. xvi., p. 5, pi. xiii., figs. 7 a, b. 



Observations. — The above species, which was described from 

 the Upper Ordo^acian (Upper Bala) of Shropshire, closely re- 

 sembles our specimen, which unfortunately is imperfect, in its 

 general features, both in outline and in the relative compression 

 of the valves. The figured specimen of P. matutina referred to 

 is a right valve, and may therefore be the more readily com- 



1 Ann. Mag. Nat. Hist., ser. 3, vol. xvi., 18C5, p. 419, pi. xiii., figs, oa, b. 



