230 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



a narrow declinous lanceolate area, and delimited on its inner aspect 

 by an ill-defined obtuse ridge extending from tlie umbo to the post- 

 ventral extremity. The inner margin of the valves is smooth at post- 

 ventral extremity. The ornamentation consists of subacute concentric 

 undulations of variable strength, and at variable distances, separated 

 by shallow concave spaces wider than the ridges ; coincident with the 

 undulations are widelj' separated linear growth-lines; the concentric 

 undulations are continued beyond the post-umbonal ridge as close-set 

 growth-lines. 



Remarks. — There is an excellent specimen to represent this species 

 with united valves in situ and possessing complete margins, rather 

 inflated and obtuse umbones, and straight ventral borders with 

 rounded extremities. The triangularity of the valves is also well 

 expressed, a shape considerably aided by tlie almost straight dorsal 

 slopes of which the posterior is much the longest. In the lanceolate 

 escutcheon-area reposes a short, thick ligament, and beneath the 

 umbones in front it is only very slightly excavated. The ornamentation 

 exhibits equidistant concentric bands of growth, with raised margins, 

 and covered with extremelj' fine, close, concentric striations. No 

 external characters are exposed. Dimensions {tvith tinited valves) : 

 length 25, height 20, diameter 10 mm. 



This species was originally regarded as marine, and doubtfully 

 associated with Platopis of Whitfi<'ld, from the Syrian Cretaceous, 

 being thought to have possible affinities with Astarte ; subsequently 

 Mr. Etheridge, jun., considered it a probable form of his genus 

 Cyrenopsis, although without knowledge of the dentition, as the 

 type showed no internal characters. My opinion, however, is that 

 the triangularity of the shell, in addition to the other external 

 characters, is more in favour of its being regarded as a Corbicula 

 than any other genus, and therefore, until further evidence is 

 forthcoming, it is proposed to include the species under that genus. 



Locality. — White Cliffs, New South Wales, 



Collection. — British Museum (Mineral Dept. 76806). 



Distribution. — Upper Cretaceous : New South Wales (White Cliffs). 



Fam. UNIONID^. 

 Unio jaqdeti, n.sp. PI. VI, Figs. 2-6. 



Description. — Shell elongately oval, narrow ; dorsal margin slightly 

 sloping to posterior extremity ; dorsal and ventral borders subparallel ; 

 umbones anterior, eroded; valves compresso-convex ; posterior region 

 produced, and slightly narrowing at end, anterior and ventral borders 

 rounded; sculpture exhibiting concentric growth-lines, crossed by 

 numerous, closely set, fine radial striations. 



Lightning Ridge. White Cliffs. 



Dimensions {icith Length . . 42 (about) 53 mm. 



closed valves). Height . . 20 22 mm. 



Diameter .12 15 mm. 



Reniarhs. — This species is represented by two specimens of some- 

 what imperfect condition, but their rarity as opalized Australian 



