MYTILUS. 143 
from the light thrown upon it through the Linnean collection 
(wherein its presence is asserted, and where one shell alone an- 
swers to its description), and from the manuscript references of 
“ List. t. 366” and “Rump. Mus. t. 46, f. D,” I entertain no 
doubt of its identity with the Mytilus exustus of Lamarck. 
This proves somewhat unfortunate, since the Lamarckian shell 
has been generally, and not unreasonably, considered the same 
as the Linnean one so named. I could almost suspect that 
Linneus had forgotten his original species when he founded 
bidens in the twelfth edition. It is a curious circumstance, that 
whilst exustus is recorded as present in his cabinet in the lst 
that accompanies the tenth edition, its name does not appear in 
the list annexed to the final one, wherein bidens was first in- 
serted. 
Movtilus nodtolus. 
Inability to discover a correct representation of the object he 
was describing caused the introduction of a diversity of species 
into the synonymy of this mussel. The original description in 
the tenth edition of the ‘ Systema’ would suit almost any mem- 
ber of Modiola proper. Of the three illustrative engravings 
there referred to, the figures of Rumphius and Argenville 
(Bradley represents Wyt. edulis) exhibit some large species with 
the general aspect of the shell (Donov. Brit. Shells, pl. 23) de- 
nominated modiolus by the writers on British Conchology. As 
such was the species understood by Gronovius, who, in that 
portion of his work at least, had not studied the twelfth edi- 
tion. Nevertheless, Argenville’s figure, though quoted as 
typical by Lamarck (hence the name Papuanus applied to our 
Northern shell) purports to be that of a New Guinea mussel 
(the older localities, however, are rarely trustworthy) ; and the 
insertion of a European shell in the work of Rumphius seems 
so unlikely, that we may perchance fancy his drawing designed 
for that closely allied congener Modiola Philippinarum. We 
learn, however, from the preface, that other objects, besides the 
great Indian collection of Rumphius, were engraved in the 
‘Thesaurus ; and from the explanatory text, that the rude 
