The animal kingdom : arranged after its organization, forming a natural history of animals, and an introduction to comparative anatomy . f the Acephala of Cuvier. The first two of these classes both possessbivalve shells; but the structure of the animal is very different, the respiration being carried on in the MOLLUSCA. 667 former oy means of four branchial leaflets, whence they are distinguished as Lameltibranchiata;whilst in the latter the function is performed by means of the mantle itself, whence they are calledPalliubranchiata. In many respects, the Conchifera are intermediate between th
The animal kingdom : arranged after its organization, forming a natural history of animals, and an introduction to comparative anatomy . f the Acephala of Cuvier. The first two of these classes both possessbivalve shells; but the structure of the animal is very different, the respiration being carried on in the MOLLUSCA. 667 former oy means of four branchial leaflets, whence they are distinguished as Lameltibranchiata;whilst in the latter the function is performed by means of the mantle itself, whence they are calledPalliubranchiata. In many respects, the Conchifera are intermediate between the other two classes;being connected with the Brachiopoda through the genera Placuna and Anumia, and with the Tunicatathrough the order Inclusa. The Conchifera and Tunicata being thus raised to the rank of classes,their primary subdivisions will be orders instead of families. CEPHALOPODA. The researches of Professor Owen upon the structure of the animal of Nautilus, and upon its rela-tions to the other Cephalopoda, have led him to propose a new arrangement of this class, which isod ct vc at b now generally adopted. The entire class. brnnchM &, Sec. i the blood iTJ(1c« intu nrn bmncbea, ab,of the gills. th(Kcreuory henr cmtractile diUtntpropel the blond through Rrspir 1 these Tciseln is divided into two orders ; of which thefirst, including nearly all existing spe- hr cies of Cephalopuds, approaches tnostnearly to vertebrated animals ; whilst thesecond, which contains only one existing °^ genus, but to which a great number offossil forms are to be referred, is more ^ closely allied to the Gasteropodous Mol-lusks. These orders are named accordingto the difference in the number of their e gills, which is one of their best marked ** characters; but they differ also in manyother particulars. Order I.—Dibbanchiata. In this order,only one gcDus, Argonaxtta, has been bitbertofound, in whicb the body is protected by anexternal shell; this consists of but one cham-ber, and docs not ad
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Keywords: ., bookauthorwe, bookcentury1800, bookdecade1840, booksubjectanimals
