Editorial note — Page 115 CHAPTER X.
Reading edition
[Footnote 16: In all the Lamp-shells the mouth is provided with two long fleshy organs, which carry delicate filaments on their sides, and which are usually coiled into a spiral. These organs are known as the "arms," and it is from their presence that the name of "Brachiopoda" is derived (Gr. brachion, arm; podes, feet). In some cases the arms are merely coiled away within the shell, without any support; but in other cases they are carried upon a more or less elaborate shelly loop, often spoken of as the "carriage-spring apparatus." In the Spirifers, and in other ancient genera, this apparatus is coiled up into a complicated spiral (fig. 67). It is these "arms," with or without Fig. 67.—Spirifera hysterica. The right-hand figure shows the interior of the dorsal valve with the calcareous spires for the support of the arms. the supporting loops or spires, which serve as one of the special characters distinguishing the Brachiopods from the true Bivalves (Lamellibranchiata).]
