The definition was not precisely similar in words to that of the 'Systema,' but the sense varied but little. It ran as follows:-- Testa oblonga, membranaceo-fragilis, basi angustata. Cardo nullus, sed valvis altero latere coadunatis ut una appareat. P. RUDIS. _P._ rugosa squamis fornicatis per seriem digestis. The name of this shell, identified (I think wrongly) by our author with the one he had termed _rudis_ in the 'Systema,' was originally _fornicata_. P. NOBILIS. _P._ squamis canaliculato-tubulosis subimbricatis. P. MURICATA. _P._ striata, squamis concavis ovatis acutis. "List. Hist. t. 370. no. 215," and "Sloan. Hist. i. p. 254," were present among the original synonyms. P. ROTUNDATA. _P._ squamis obsoletis, testæ margine rotundato. P. SACCATA. _P._ nuda saccata erectiuscula. P. DIGITIFORMIS. _P._ nuda digitiformis incurva. P. LOBATA. _P._ nuda lobata. * * * * * In addition to the printed species, an anomalous _Pinna_, which I doubt not was the _Lingula anatina_, is here described. P. VIRIDIS. _P._ ovalis, basi compressa. Generis dubii huc relata, donec certiora determinentur. Testa utraque ovali-oblonga, viridis, intus magis pallida; quasi compressa, et fere naviculata, acutior. ARGONAUTA. The intended name of this genus was _Cymbium_, the one applied to it by Gualtieri. A. ARGO. _Cym._ carina dentata. "Bonan. 1. f. 13," and "Klein, 3. t. 1. f. 3," were the unprinted synonyms. The intended specific epithet was _C. papyraceum_. NAUTILUS. There was no definition of either this, or of the preceding genus, in the written catalogue. N. POMPILIUS. _N._ apertura cordata, anfractibus contiguis. The unprinted synonyms were "Bonan. 1, f. 1, 2," "Breyn. Polyth. 14," "Pet. Amb. t. 3. f. 7," "Pet. Gaz. t. 99. f. D," "Klein, 2. t. 1. f. 1, 2," and "Bellon. Aquat. 318. t. 382." Seba was not quoted. N. SPIRULA. _N._ apertura orbiculari, anfractibus distantibus. The I in the reference to Rumphius was a misprint for the written 1; "Bon. 1. f. 39," "Breyn. Polyth. 21. f. 2," "Klein, 5. t. 1. f. 6," and "Petropol. Mus. 532. n. 6," were the unprinted synonyms: "tubo" was an emendation. CONUS. Testa oblonga, cylindrica, deorsum attenuata. Apertura longitudinalis. Labium edentulum. Os non reflexum. Columella integra. This most natural genus had the precise limits ordinarily assigned to it. C. MARMOREUS. _C._ conicus fuscus, maculis ovatis albis. "Bonan. 3. f. 123" was an additional synonym; the "versus basin transverse striata," and "subtruncata, apice prominulo," with the account of the variety, were not found in the MS. C. IMPERIALIS. _C._ pictus fasciis flavis cingulisque linearibus albo fuscoque articulatis. The "obconica" was simply "conica"; there was no description of the spire. C. LITERATUS. _C._ conicus albus punctis fuscis. The spire was not described: the reference to d'Argenville was I, not _Q_. C. VIRGO. _C._ striis convexis lævibus, basi cærulescente.