212 C. F. LASEROX. 



impression, which does not however extend entirely across 

 the valve. The sculpture is concentric, and the surface of 

 the test is ornamented with a number of equidistant shallow 

 growth folds. This ornamentation is continuous upon the 

 truncate anterior margin, bending at an acute angle up- 

 wards towards the umbos. 



Dimensions. — Breadth 2 inches; height 1^ inches; thick- 

 ness of united valves probably under £ an inch. 



Loc. Burrier (D). 



Hor. Wandrawandian Series. 



Obs. Only two specimens of this most remarkable shell 

 were found, and these were on the one slab. One is a 

 nearly perfect internal cast of aright valve, and the other 

 is a testiferous left valve. It is named in honor of Mr. 

 W. S. Dun, Palaeontologist to the Mines Department. 

 Astartila polita, Dana. (Amer. Jour. Sc, 1847, IV, p. 155) 



Loc. Shoalhaven River (A). 



Hor. Wandrawandian Series. 



Obs. Several internal casts were found in this locality. 

 Astartila (Pachydomus) sp. (Type A.) 



Specific Characters.— A medium sized shell, nearly cir- 

 cular in outline and inflated ; anteriorly viewed, elongate 

 cordate. Umbos prominent, anteriorly situated and 

 recurved. Hinge line curved and posterior to the umbos, 

 with a well marked, elongated external (opisthodetic) liga- 

 ment. Adductor impressions unequal; the anterior the 

 more prominent, rounded ventrally, and straight on the 

 dorsal margin; the posterior shallow. Situated above the 

 anterior muscular impressions are two smaller but sharply 

 defined impressions, which served for the attachment of 

 the pedal muscles. Pallial line simple and well marked. 

 Hinge line of right valve provided with one large cardinal 

 tooth, fitting into a corresponding socket on the left valve. 



