Dentalium. Patella. Nerita. Helix. Turbo. Trochus. Turricula. Buccinum. Lyra. Morion. Conus. Voluta. Strombus (not that of the 'Systema'). Harpago (=Strombus). Murex. Cassida. Cypræa. Bulla. Haliotis. Nautilus. Cymbium (=Argonauta). Spondylus. Ostrea. Pecten. Arca. Pinna. Mytilus. Solen. Tellina. Chama (not that of the 'Systema'). Cunnus (=Venus). Pholas (not that of the 'Systema'). Trunculus (=Donax). Bucardium (=Cardium). Besides the four genera (_Chiton_, _Lepas_, _Teredo_, _Sabella_) that were excluded from this catalogue, either from the absence of specimens, or from mistrust of their being veritable Testacea, six of the remaining 32, namely, _Pholas_, _Mya_, _Mactra_, _Chama_, _Anomia_, and _Serpula_, were likewise omitted, not being yet eliminated from _Solen_, _Bucardium_, _Spondylus_, _Ostrea_, and _Dentalium_. To counterbalance these, we find no less than eight subsequently abandoned groupings: _Turricula_ (an undefined amalgam of the long-spired species of _Buccinum_, _Murex_, and _Strombus_). _Lyra_ (the _Harpa_ and _Purpura_ of the Lamarckian school). _Morion_ (an unnatural compound of _Eburna_, _Auricula_ proper, _Pythia_, _&c._). _Strombus_ (a combination of the immature members of the received genus with _Pyrula_, _Fasciolaria_, and other allied forms). _Cassida_ (nearly the modern _Cassis_). _Pecten_ (equal to _Lima_ and _Pecten_). _Chama_ (the _Tapes_ of recent conchologists). _Pholas_ (chiefly composed of _Artemis_ and _Lucina_). It may be remarked, moreover, that the simple univalves commence, and the bivalves close the series; the exact converse of the order in which they are marshalled in the two principal editions of the 'Systema Naturæ.' I feel assured, after a careful study of the manuscript, that the names eventually allotted to the shells of the 'Museum' did not result from a careful comparison of the royal specimens with the typical examples in the private collection of our author, but were attached to the species, either from the identity of the written and printed synonymy, or from the general accordance of their described features with the meagre characteristics enumerated in the prior publication.