142 SPECIES OF THE SYSTEMA. 
the “ cardo absque denticulo” of the ‘Museum Ulrice,’ and 
the mention of a larger tropical form, it is not unlikely that the 
specimen there described was a different species: the denticles, 
however, are very minute, and usually concealed by the over- 
lapping of the epidermis. 
Hoytilus ungulatus. 
By the addition of a reference to Lister, whose figure has 
been quoted for canalis by Lamarck, and of a tropical locality, 
Linneus, in the twelfth edition of his ‘ Systema,’ has confused 
the Mediterranean shell, which he had doubtfully constituted 
(“an varietas prioris”’) in his earlier edition. Of that shell two 
marked specimens are still preserved in his collection, one a 
large distorted and greatly incurved example of edulis; the 
other, which we have here delineated (pl. 2, f. 4), that large 
South European form of the same variable species, which has 
been termed Galloprovincialis by Lamarck. The quoted figures 
of Gualtier bear much likeness to the specimen delineated; the 
engraving of Regenfuss represents the same species, but is still 
nearer to the typical edulis. 
Mytilus Hidens. 
Born, in the synonymy attached to his Mytilus bidens, has 
confused at least three species, M. Magellanicus, exustus, and 
niger; the two latter of these are, however, excluded by the 
expression “ sulcata,’ and by the magnitude (nearly two inches) 
attributed to the mussel in his description; Schréter, Gmelin, 
and Dillwyn have similarly appropriated this name to the Myti- 
lus Magellanicus of Chemnitz. Deshayes, who comments on 
the absurdity of identifying a large purplish coarsely-grooved 
South American shell with a small ashy-horn coloured simply 
striated Mediterranean one, observes that the description, un- 
accompanied as it is by any illustrative synonymy, is utterly 
insufficient for the positive determination of the species. As 
the species stood, I fully coincide with him in this opinion, but 
