E id the Family Osteodesmacea. 133 È 
neously considered by him as that of A. myàlis, and the 
type of Osteodesma, where he remarks, “ une sorte de 
. gaine qui entoure une sorte de repli de manteau, contient 
losselet cardinal.” It is difficult to account for such | 
glaring discrepancies in notes on the same species, only - 
five pages apart. The sole way in which it appears 
possible to reconcile or clear up these conflicting state- 
ments is, by assuming that the species examined by M. 
de Blainville was not A. myalis, but that M. Des- 
hayes, while he perceived that the former was in error 
respecting its generic character, was not aware of his 
having mistaken the species also; and that the contra- 
dictions relative to A. myalis, in his own notes on La- 
marck, occurred through inadvertence ; they having, 
perhaps, although printed together, been written at long 
intervals. | 
In this assumption, with regard to M. de Blainville, _ 
at least, we are fully borne out by is description and 
figure, as well as his remarks. He states, pp. 564, 660, 
that he had never seen either A. myális itself, or a figure 
of it, and suppresses it, p. 659, under the impression 
that the shell before him, a true ‘Periploma, was that 
species. His description, however, is wholly irrecon- 
cilable with Lamarck's, who says A. myalis resembles 
Mya arendria externally, is even larger and rather solid, 
although semi-transparent. M. de Blainville, on the 
contrary, speaks of his shell as exceedingly thin and 
fragile. His description is closely applicable to A. 
trapezoides, Lam., of which he gives a figure in con- 
nection. After rais» viewing the case, therefore, in 
all its bearings, the conclusion appears irresistible, that 
the error of M. de Blainville arose from the shell - 
