200 Proceedings of the Royal Society of Victoria. 



anterior third. Anterior margin rounded on the ventral angle ; 

 obliquely rounded dorsally, having a marginal flange which is 

 feebly corrugated. Carapace thickening towards the posterior 

 extremity and becoming steep in front of the sub-acute posterior 

 area. Surface swollen and somewhat lumpy, with indications of 

 shallow pittings. Hingement showing the characteristic thin 

 ridge, which tits into the furrow of the opposite (right) valve ; 

 tooth and fossa obscure. Length of valves, 0.6 mm.; greatest 

 height, 0.3 mm.; thickness of carapace, 0.26 mm. 



Ajfi7iities. — At tirst sight the shape of the species reminds one 

 of Cytheridea trapezoidalis, Terquem,^ but the form of hinge in 

 the latter species is clearly that of a Cytheridea. Cythere har- 

 risiana, Jones,- of the English cretaceous, also bears a general 

 resemblance to our form in its outline, but the tumid portion of 

 the posterior region in the latter is more oblique. 



Occurrence. — One example (represented by a left valve) ; 

 Jurassic, Greenough River district, West Australia. [2150.] 



Cythere corrosa, Jones and Sherborn, var. grossepunc- 



tata, var. nov. (PI. XXIII., Figs. 5, 5«, bb.) 

 Descriptive remarks. — The above variety is distinguished from 

 the type form,'* which was found in the fuller's earth oolite of 

 Midford, near Bath, England, essentially in its more elongate 

 carapace, and coarser and fewer pittings. The anterior flange- 

 like margin is corrugated in this variety, and the posterior 

 flange is striate. 



Measurements. — Length of valve, 0.7 mm.; greatest height, 

 0..32 mm.; thickness of carapace, 0.32 mm. 



Occurrence. — Fairly common ; Jurassic, Greenough River dis- 

 trict, West Australia. [2151.] 



Genus Loxoconcha, G. 0. Sars. 

 Loxoconcha elongata, sp. nov. (PI. XXIIL, Figs. 2, 2a, lb). 



Specific characters. — Carapace, as seen from the side, elongate, 

 ovate, flexuous in outline ; with a sharply rounded, antero-ventral 



1 Mem. Soc. Geol. France, ser. 3, vol. iv., 1885, p. 31, pi. iv., figs. 20(i-c. 



2 See Jones and Hinde, Suppl. Mon. Cret. Kntoni. (Pal. Soc), 1890, p. 16, pi. i., figs. 

 47-52. 



3 Jones and Sherborn, Proc. Bath. Nat. Hist, and Aiitiq. F. Club, vol. vi., 1888, No. 3, 

 p. 254, pi. ii., figs. 12(i-c. 



