237 
Helations and Differences. — I know of only one species resembling 
this one in the number and simplicity of its radiating folds, and that is 
A, flexuosus, McCoy, which differs especially by the great depth of its right 
valve. 
Dorizon and Localities.— One, specimen was found in a greyish-black 
sandstone at the foot of Harper’s Hill, in a railway cutting. 
Aviculopecten Pittoni, J. Morris. 
PI. XXI, Pig. 4. 
Decten FHtoni, J. Morris, 1815, In Strzeleclii’s Phys. Descr. N. S. Wales and V. D. Land, 
p. 277, pi. 14, fig. 2. 
This is an orbicular, convex shell, capable of reaching a very great 
size. Its ears are subequal, the anterior being only a little more rounded at 
the extremity than the posterior. The surface is ornamented with fourteen 
or fifteen thick radiating folds, each formed by the union of from three to 
five small granular folds, travelling parallel with each other towards the 
margins ; at the bottom of the furrows, which separate the folds, and are of 
the same width as the folds, are found small ribs like those which served to 
form the whole of the large folds. These are the characteristics of the right 
valve, the only one which Mr, Morris and I have seen. 
Dimensions. — Judging from a very poor imperfect sj)ecimen this 
species can acquire a length of twelve centimetres. The ordinary specimens 
have more modest dimensions ; one of these, an internal cast, is only five 
centimetres long, and about as broad, its thickness being about one centi- 
metre. 
Delations and Differences. — This species differs from A. comptus, 
J, Dana, by the smaller numher of its radiating folds and their relatively 
greater width. Instead of fourteen or fifteen folds, A. comptus has twenty 
or twenty-two. 
Horizon and Localities. — Two internal casts of this species were found 
in a reddish sandstone, one at Musclebrook, the other between Muree and 
Morpeth. The specimen described by Mr. J. Morris was found at Mount 
M^ellington, Tasmania. 
