Foraiuinifera and Ostracoda. 203 



Measurements. — Length of valve, 0.67 mm.; height, 0.5 mm.; 

 thickness of carapace, about 0.46 mm. 



Occurrence. — One valve ; Jurassic, Greenough River district. 

 West Australia. [2154.] 



Genus Cyiheropteron, G. O. Sars. 



Cytheropteron austral iense, sp. nov. (Plate XXIII., 



Figs. 7, la, lb). 



Specific characters. — Valves elongate-ovate, surface rising from 

 the depressed dorsal area to a swollen or even ridge-like promin- 

 ence along the ventral border ; the summit of the ridge is in the 

 middle of the ventral line, and its edge slopes away in a bold 

 curve towards the antero- and postero-dorsal margin. Both 

 extremities of valve rounded and depressed. Surface of valve 

 marked with faint concentric striae, formed of interrupted pittings 

 running parallel with the edge of the ventral prominence, and 

 curving round to enclose the central area. Indications of the 

 muscle attachments are seen as a cluster of five minute ovoid 

 depressions, almost in the position of the median sulcus, which is 

 often present in this genus. 



Measttrements. — Length of valve, 0.57 nmi.; greatest height, 

 0.3 mm.; thickness of carapace, 0.3 mm. 



Affinities. — The nearest allied form to the above species seems 

 to be Cytheropteron concentricum, Reuss sp., and especially its 

 variety virginea, Jones.' C. australiense differs from these 

 mainly in the squarer form of the valve as seen from the side, 

 the more ridge-like ventral prominence, and the rhomboidal edge- 

 view of the carapace. It is, however, closely allied to Professor 

 Jones's variety above referred to, and further specimens from 

 Australia may show a still nearer relationship. It is worth 

 noting in connection with the age of the above form and its allies, 

 that the variety virginea had its range extended into the 

 neocomian by the present author's discovery of the rich microzoic 

 fauna of the Bargate beds in Surrey. 



Occurrence. — A specimen with united valves ; Jurassic, Green- 

 ough River district, West Australia. [2155.] 



1 See Jones and Hiiide, .Suppl. Mon. C'ret. Entom. (Pal. Soc), 1890, p. 32, pi. i., %8. 

 li-17. 



2a 



