12 
valve more convex than the right, lie further states that for a third of the 
l)readth in the left [right], or less convex valve, towards the ventral margin, 
the surface is depressed and nearly Hat. 
In referring the fossils figured by Dana and Do Koninck to the 
])resent species, rather than to Vecten illawarrenus, INIorris, avc are inlluenced 
hy the following considerations : — (1) This is the only large Paheopecten 
Ave are ac(piainted Avith from Harper’s Hill ; (2) the same locality Avas giA^en 
by both the above authors ; (3) Ave have never seen any shell that could 
satisfactorily he referred to P. illmoarrensis from the Hlawarra ; (4) the 
outline of A. 3Iitchelli is longitudinally-oval, as opposed to the broad 
transAU'rsely-oval outline shoAvn in ]\Iorris’ figure, notwithstanding that it 
represents only portion of a vah'e ; (5) both Dana and I)e Koninck represent 
such a longitudinally-oval, pauci-costate form. 
The conclusion Ave have arrived at is, therefore, that Dana’s identitica- 
tion is incorrect, and De Koninck Avas misled thereby, for it is certain, as far 
as it reasonably can be, that both described similar shells. The only point 
of discrepancy betAveen the valves knoAvn to us and Do Koninck’s figure of 
the same is that in the latter some of tlie costm are bifurcate, whilst in ours 
they are iuA^ariably simple. 
IVe name this Aviculopecten in honour of Sir T. L. Mitchell, at one 
time Surveyor-General of this State, Avho Avas the first to collect fossils 
at the historic locality of Harper’s Hill during one of his memorable 
exploratory expeditions in 1831 in search of the “ Kindur” RiA'er.^ 
Localities and Horizon. — Portion 217, Parish Pokolbin [C. Cullen)-, 
Harper’s Hill ; one mile north of Comerford’s Quarry, "West IMaitland 
(P. IF. Fdgeioorth Laeid) ; Allandale {C. Cullen)-, Portion 18, Parish 
Allandale (G. Cullen)-, Portion 33, Parish Pokolbin {C. Cullen)-, Jones’ 
Selection. Cranky Corner, Portion 8, Parish Stanhope, County Durham 
{JF. S. Dun)-, Allandale Eoad (G. A. Silssmilch). — Permo-Carboniferous — 
LoAver Marine Series. 
Collections. — Mining and Geological Museum, Australian Museum, 
and Geological Dept., Technical College. 
’ Mitchell — Three Expeil. Int. E. Austr., 1838, I, p. 14. 
