The Cambridge natural history . are situated at the front edge of the mantlemargin. Shelly matter is deposited, and probably secreted, not only bythe mantle, but also in some genera by the foot. This is certainlythe case in Cyml)turn, Olira, Ancillnria, Cassis, Distortio, andothers, in several of which tlie foot is so large that the shellappears to be quite immersed in 1 See also p. 258. - J. E. Gray, rhil. Trans. 1833, p. 771 f. 256 SCULrTURE AND ORNAMENTATION The deposition of shell is not continuous. Eest periods occur,during which the function is dormant; these periods are markedoff o
The Cambridge natural history . are situated at the front edge of the mantlemargin. Shelly matter is deposited, and probably secreted, not only bythe mantle, but also in some genera by the foot. This is certainlythe case in Cyml)turn, Olira, Ancillnria, Cassis, Distortio, andothers, in several of which tlie foot is so large that the shellappears to be quite immersed in 1 See also p. 258. - J. E. Gray, rhil. Trans. 1833, p. 771 f. 256 SCULrTURE AND ORNAMENTATION The deposition of shell is not continuous. Eest periods occur,during which the function is dormant; these periods are markedoff on the edge of the shell, and are known as lines of some cases {Murex, Triton, lianella), the rest period is markedhy a decisive thickening of the lip, which persists on the surfaceof the shell as what is called a varix (see p. 26-)). The various details of sculpture on the exterior surface of theshell, the striae, rihs, nodules, imbrications, spines, and otherforms of ornamentation arc all the product of similar and.
Size: 1178px × 2120px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
