C. UNEDO. _Buc._ subcordatum, sulcis lunulis coloratis. C. MURICATUM. _Buc._ subrotundum sulcatum, lateribus muricatis. C. MAGNUM. _Buc._ oblongum, sulcis angulatis latere serratis. I had hoped to have found the 19 a misprint, but the MS. and the printed copy agree precisely in every particular. C. FLAVUM. _Buc._ subovatum sulcatum, latere altero scabrum, altero dentatum. The redundant "subovata" was not in the copy, where the remark was made that the species resembled the shell subsequently termed _Chama cor_, the figure of which (Gualt. t. 71. f. E.) had been cited, but erased in the MS. The ideal hence derived is a very different shell from the one supposed identical. No mention is made of lateral teeth: was it then a veritable _Cardium_? C. LÆVIGATUM. _Buc._ ovatum, striis læviusculis longitudinalibus. I do not consider this (the _B. striatum_ of the MS.) to be identical with the _C. lævigatum_ of the 'Systema.' C. SERRATUM. _Buc._ ovale læve, antice serratum. "Ovata" stood in the place of the printed "obovata": "curvatus" and "parvi" were subsequent to the MS. C. TRISTE. _Buc._ ovatum læve, rima anoque obsolete striatis. The 'Museum' was referred to for this shell previously to the publication of the details. Curious to relate, the species was wholly omitted in the twelfth edition of the 'Systema.' It was, in all probability, a _Mactra_, which genus had not been constituted at the period when the description of _C. triste_ was issued. C. PECTINATUM. _Buc._ subcordatum, striis hinc longitudinalibus, illine transversalibus. The erroneous reference to Gualtieri was not present in the written copy. * * * * * Mention was made in the 'Systema' of a _Solen bullatus_, for a more detailed account of which the reader was referred to the 'Museum Ulricæ.' No such species appeared in the published edition; but the omitted shell (a veritable _Cardium_) was thus described in the unprinted version:-- BUC. BULLATUM. _B._ subrotundum, antice crenato-hians. Rump. 143. t. 44. f. N. Pecten bullatus. Testa subrotunda, inflata, gibba, fragilis, pellucida, substriata, rufo nebulosa, antice hians, margine serrato. Umbones tumidi, obtusi, reflexi. Rima minima brevissima. Ani regio obsoleta. Dens cardinis fere unicus, minimus. Marginales solitarii, remoti, compressi, majores. DONAX. TRUNCULUS was the proposed name of this genus, which was thus characterized:-- Testa compressa, antice obtusissima, retusa. Cardinis dentibus 2, marginis unicus. D. SCORTUM was wisely omitted. D. PUBESCENS. _Trun._ antice spinis ciliatus. D. RUGOSA. _Trun._ antice rugosus, marginibus crenatis. The printed "cuneiformis" has replaced the earlier "majuscula"; and "crenulatis" was originally "undulatis." "Intus subviolacea est" was not in the written copy. D. TRUNCULUS. _Trun._ antice lævis, marginibus crenatis.