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the Family Osteodesmacea. 
pretnuis, and of his Anat. preténuis, p. 48, of his Bi- 
valves. If Dr. Turton was correct in judging his A. 
declivis to be distinct, it is evident that M. preténuis 
should be struck from the synonymy in his Dictionary. 
He also refers to tab. 18, f. 3, Wood, Gen. Conch., fig- 
ured as the young of M. declivis, Penn., and to tab. 1, 
f. 2, Mont. Test. Brit., for figures of his A. ddis. 
It is impossible, without reference to the very shells 
which were before the authors, to clear up or decide 
upon confusion like this. 
apt. Brown, in his Conch. Ilust. of Great Britain 
and Ireland, represents, tab. 11, f..6, under the name of 
Anat. villosidscula, a shell chasis resembling Mr. Mon- 
tagu’s figure in all but the form of the tooth, and refers 
it to McGillivray, Phil. Journ..tab. 1, f. 10, 11. This 
latter work is not accessible to me, but if Capt. Brown’s 
figure may be-relied upon, and considering his remark 
that it has usually been. mistaken for the young of M. 
declivis, (T. pubéscens), there is every reason for be- 
lieving it a true Thracia. It may possibly be identical 
. with Dr. Turton’s A. declivis. Capt. Brown's figure 
might, at first sight, be mistaken for à representation of 
Th, similis, Nobis, but it will be observed, that the an- 
terior extremity is the longer, instead of the posterior, as 
in that species. 
With regard to Mya (Ligula) distórta, Montagu, tab. 
l, f. 1, referred to by M. Kiener, for T. corbuloides, - 
Deshayes, I suspect it will be eventually. found to 
belong among the perforating Corsgsutæ, to which I am 
also inclined to refer Anatina truncata, Turton, British 
Biv. p. 46, tab. 4, f. 6, both species having similar 
habits of burrowing i in the limestone X the British coast. 
