. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 176 PTEROPODA. are hollow, and that their cavities communi- cate with the common cavity of the head: they have likewise their proper muscles, and each receives a large nerve derived imme- diately from the anterior supra-oesophageal ganglion. As to the use of this elaborate apparatus, there is still room for speculation. Captain Holboll, although he frequently ob- served them porrected, while the creature was swimming, never saw them employed as suckers or instruments of prehension ; never- theless, it seems impossible to
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 176 PTEROPODA. are hollow, and that their cavities communi- cate with the common cavity of the head: they have likewise their proper muscles, and each receives a large nerve derived imme- diately from the anterior supra-oesophageal ganglion. As to the use of this elaborate apparatus, there is still room for speculation. Captain Holboll, although he frequently ob- served them porrected, while the creature was swimming, never saw them employed as suckers or instruments of prehension ; never- theless, it seems impossible to doubt that such is their real office, when we reflect upon their remarkable structure, and further take into account their situation, so completely analo- gous to that occupied by the sucking discs of the Cephalopoda, and still more closely re- sembling the cephalic appendages of Pneumo- derma. It is, therefore, extremely probable that these organs are employed for holding to foreign objects at the bottom of the sea, and that the great number of the sucking discs is in correspondence with the power possessed by the Clio of crawling about upon uneven surfaces. The mouth of the Clio is a vertical fissure, that is easily displayed by slightly folding back the head-cones (fig. 110. 13, w). Its margins seem to enclose some calcareous substance, which, in specimens preserved in spirit, is of a chalky whiteness. Numerous muscular fasci- culi surround this opening, which, when ex- panded, has somewhat of a triangular form, so that during life the mouth can be forcibly opened by the radiating muscular fasciculi that surround it. In the cavity of the mouth there may be observed, on each side, a round fossa, in which can be seen projecting, even with the naked eye, a hard shining substance, first noticed by Pallas and Fabricius, who re- garded these bodies as simple teeth. Closer inspection, however, reveals them to have a very curious structure, which is, perhaps, unique, each consisti
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