The Cambridge natural history . 402 POLYPLACOPHORA. diverge from the neighbourhood of the median heak or umbo. The space enclosed between these ribs is known as the median area or jugum, the other twospaces as the lateral areas or?pleura. The ribs terminate withthe edge of the tegmentum, andare not found on the articula-mentum. In certain genera theseareas are either non-existent, orare not distinctly marked. Thesculpture of tlie lateral areas (whichis, as a rule, much stronger thanthat of the median area) willgenerally be found to resemblethat of the anterior valve, whichhas no proper median
The Cambridge natural history . 402 POLYPLACOPHORA. diverge from the neighbourhood of the median heak or umbo. The space enclosed between these ribs is known as the median area or jugum, the other twospaces as the lateral areas or?pleura. The ribs terminate withthe edge of the tegmentum, andare not found on the articula-mentum. In certain genera theseareas are either non-existent, orare not distinctly marked. Thesculpture of tlie lateral areas (whichis, as a rule, much stronger thanthat of the median area) willgenerally be found to resemblethat of the anterior valve, whichhas no proper median area. Inthe posterior valve the median Fig. , fourtli, and eighth area is very small, while the sculp-valves of a Chiton, showing Li, ture of the rest of the valve cor- laminae of insertion ; n, n, notches ; i j. i 5.^, , suturai laminae, x 2. rcsponcls to that ol the lateral areas generally (see Fig. 261). The articulamentum of the intermediate valves is divided intotwo equal parts in the middle of the anterior edge, opposite tothe
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
