A treatise on malacology; or, Shells and shell fish . e greater facility of nomenclature,we shall designate under the following sub-genericnames:— 1. Unio: the bosses or umbones prominentand tumid, the circumference and the posterior hinge mar-gin never angulated, and both thecardinal teeth very muchreceding from the anterior margin, as in U. MytiloidesRaf., and all such species or varieties. 2. Cunicula, wherethe umbones are even larger, but not tumid, being, as itwere, compressed or flattened : the shell is generallyoval, or angulated at the base of the posterior side; —examples, C. planulat
A treatise on malacology; or, Shells and shell fish . e greater facility of nomenclature,we shall designate under the following sub-genericnames:— 1. Unio: the bosses or umbones prominentand tumid, the circumference and the posterior hinge mar-gin never angulated, and both thecardinal teeth very muchreceding from the anterior margin, as in U. MytiloidesRaf., and all such species or varieties. 2. Cunicula, wherethe umbones are even larger, but not tumid, being, as itwere, compressed or flattened : the shell is generallyoval, or angulated at the base of the posterior side; —examples, C. planulata, cuneata, purpurata, Lam., &c.:the outer cardinal tooth slightly diverges from the base of the inner. S. Ligumia : theform is particularly long, likethat of Iridina, the umbonessmall and retuse, and the car-dinal teeth close to the ante-rior end ; as in U. recta Theliderma: the form isvarious, but the posterior hingemargin is generally elevatedand angulated, and the outsideof the valves tuberculated orgranulated, — a character not. distinct species sent from that country, evidently labelled by the same hand,yet bearing the same specific name. Mr. Leas Synopsis leaves this partof the subject almost as obsure as ever, because he merely cites the name,without giving any reference to the works of the authors he quotes. Byhis plan, as novel as it is detrimental to science and all critical inquiry,the author (no doubt, unintentionally) imposes an effectual bar to the ve-rification of his own nomenclature, no one here being acquainted with allthe detached papers on these shells printed in America. 268 SHELLS AND SHELL-FISH. PART I. found in any other of these groups* (T. Jig. 50.). 5. Potomida: the shell rather shortand oval; the umbones prominent, but not so large asin Unio ; the outer surface smooth ; the cardinal teeththick, perpendicular, but the outer one diverging. Theseare mostly European shells, and are represented by U. si-niiata Lam., and our P.
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectmollusks, bookyear184
