MYTILUS. Yi 
not exhibit the required characters, easily effected the early re- 
cognition of this large and strongly-featured oyster. It is the 
Ostrea hyotis (Chemn. Conch. Cab. vol. vii. pl. 75, f. 685) of 
authors. Specimens exist in the Linnean cabinet, but are 
devoid of authority, since the species is not mentioned in the 
list of its original contents. 
SMUptilus frows. 
The figure of Argenville is so characteristic, and agrees so 
correctly with the original description in the ‘Systema,’ that 
the species being thus pictorially defined was early recognised 
by Born. Even now, I know of no better engraving than the 
one cited by our author (Argeny. Conch. ed. 1, pl. 22, f. D). 
From the polymorphous nature of the shell, it has been sepa- 
rated in Lamarck’s ‘ Animaux’ into three suppositious species, 
O. rubella, O. limacella, O. doridella, all which must again be 
reunited as Ostrea frons. I speak more boldly upon this point, 
from a long study of that most difficult genus Ostrea, and the 
comparison of a vast number of specimens. From the expres- 
sion “ nigra,” in the ‘Museum Ulrice,’ one may doubt as to the 
identity of the species there described: it was perhaps that 
variety of O. crista-galli in which one of the lips only is sca- 
brous. 
sivtilus margaritiferus. 
The language of the ‘Museum Ulvice’ leaves no doubt of 
the identity of this species with the Meleagrina margaritifera of 
Lamarck’s ‘ Animaux sans Vertébres.’ Upon this all writers 
are agreed ; the misfortune, however, is, that both writers con- 
fused more than one species under the same appellation. “In 
utriusque Indiz oceano ” is the habitat given in both editions 
of the ‘Systema;’ the locality list of Lamarck embraces both 
Ceylon and Mexico. Now there are two very distinct species, 
at the least; one of a rich pure dark green, with flat white im- 
bricated scales (Chemn. Conch. Cab. vol. viii. pl. 80, f. 718), the 
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