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rings of growth. The ears are striated, the anterior ear rounded and cleanly 
separated from the rest of the shell by a well-marked sinus ; the posterior ear 
is small and rectangular. The length of the hinge line is less than the long 
diameter of the valves. 
Dimensions. — The length and breadth are both fifteen millimetres. 
Relations and Differences. — It differs from the preceding by its more 
rounded form, and by the ornaments of its ears ; and from A. Icevigatus, De 
Koninck, by the shape of its ears, and by being thinner. 
Horizon and Localities . — It is rather abundant in the limestone of 
Ireland, but rare at Burragood, N. S. Wales. 
Aviculopecten elongates, F . McCoy. 
PL XXII, Pig. 5. 
Recten elongatus, P. McCoy, 1844, Sjnop. Carb. Poss. Ireland, p. 92, pi. 16, fig. 9. 
This is a medium sized, transverse, oval, rather regularly ventricose, 
sub-equivalved shell. Its ears are small, the anterior ear well defined, and 
the posterior ear united to the main body of the valve by a very gentle curve. 
To the naked eye the surface appears smooth, but with a lens concentric rings 
of growth are perceptible. 
Dimensions. — The length is thirty-six, breadth forty, and thickness 
twenty-three millimetres. 
Relations and Differences . — In general form this species resembles 
A.filatus, McCoy, but it differs by having no radiating stria3. I have been 
able to determine the Australian specimens accurately by comparing them 
with specimens from Ireland. 
Horizon and Localities. — In Ireland it is found at Millecent, in 
Australia at Wollongong. 
Aviculopecten ptychotis, F. McCoy. 
Recten ptychotis, p. McCoy, 1847, Ann. Mag. Xat. Hist., XX, p. 298, pi. 14, fig. 2. 
This shell is small, oval, transverse, slightly ventricose, with a perfectly 
smooth surface. Its beaks are small and rather pointed. The ears are 
unequal, the anterior ear is rather narrow and divided from the rest of the 
