205 
Dimensions. — One of the best specimens sent me measures 8'5 centi- 
metres long, 4' 5 broad, and four thick. The distance between the beaks and 
the anterior margin is about three centimetres. 
Delations and Differences. — This species is closely related to clava, 
McCoy, from which it differs by its relative proportions, and by the much 
less anterior position of its beaks. 
Horizon and Localities .—Mx . J. Dana found this species at Wollon- 
gong Point and Illawarra ; Mr. W. B. Clarke at Mount Vincent, and 
Burragood on the Paterson, in a greyish sandstone. 
Sangtjinolites mitchellii, L. G. de Koninch} 
PI. XVJ, Pig. 3. 
This is a moderate-sized, gibbous, inflated, nearly oval shell, only 
about one-third longer than broad. Its hinge line is almost straight, while 
its ventral edge is arched and slightly sinuous towards its anterior third ; the 
anterior margin is regularly rounded, while the posterior, which is much 
larger, has a very irregularly curved outline. The posterior side is decidedly 
gaping. The beaks are thick, recurved so as nearly to meet, and placed at 
about the anterior two-fifths of the shell. The whole external surface is 
covered with irregular concentric wrinkles of growth. The muscular 
impressions have left scarcely perceptible traces on the internal casts which I 
have examined. 
Dimensions . — The length is six, the breadth three and a half, and the 
thickness four and a half centimetres ; and the distance of the beaks from 
the anterior margin is eleven millimetres. 
Delations and Differences. — This species, which I dedicate to Colonel 
Mitchell, one of the brave Australian explorers, differs from the preceding by 
its much smaller size, its gibbosity, and the less central position of its beaks. 
Horizon and Localities . — Two specimens of this species were found 
by Mr. W. B. Clarke, one in a brownish limestone at Afilalong, and the 
other in a white limestone at Wollongong. 
I [Compare Sangidnolites cf. Mitchellii, Waagen, Salt Range Fossils (Pal. Iiidica), IV, Pt. 2, 1891, p. 
127, t. 5, f. 4a, b, c. W.S.D.] 
