108 SPECIES OF THE SYSTEMA. 
culum”’ (the flatter valve) than in the “fornix” (the more 
convex one). 
Practically, the pellucens may be said to be erased from our 
catalogues, for no further notice is taken of it in the recent 
Monographs of the genus Pecten than to enumerate it among 
the undetermined species. 
Ostrea obliterata. 
The Pecten recognised by conchologists for this species is 
the P. obliteratus of Sowerby’s Monograph (Knorr, Délices, 
pt. 5, pl. 21, f. 6). It was determined chiefly by the details 
communicated in the ‘Museum Ulrice, and the indicated 
affinity with pleuronectes. Gualtier’s figure is very rude, but is 
usually quoted for the species. Our author did not himself 
possess it. 
Ostvea sanguinea, 
Gualtier, in the cited engraving, has delineated a Pecten, 
but so rudely that the species cannot possibly be determined : 
neither, indeed, do the details of the ‘Museum Ulrice’ suffice 
for the recognition of a member of so populous a genus as 
Pecten. The “semiaurita” of the diagnosis is a somewhat 
enigmatical expression, and might either mean having ears on 
one side (yet scarcely so, for our author uses “ uniaurita” for 
that peculiarity), or having small-sized auricles: the “ auricule 
pares,’ added in the revised copy, would indicate the latter 
meaning. 
Of the shells in the Linnean cabinet, the Pecten senator 
(Chemn. Conch. Cab. pl. 65, f. 617, not well) agrees, by far, 
the best with the definition, and as the type of O. sanguinea is 
stated to be present in the Linnean collection, there is every 
reason for believing it was that species which was actually 
intended. Nevertheless, the substitution of the earlier appel- 
lation for the clearly characterised senator is scarcely to be 
urged, for unless the term “semiaurita” should be understood 
