. Natural history. Zoology. 6i6 AJOLLUSCA—APLACOPHORA. In some forms the animal is very long in the body and the shelly plates are placed at intervals. The animals, which are vegetable feeders, may be found clinging, lilce limpets, to the under surfaces of rocks and stones at low tide, and when detached will coil up much after the fashion of the well-known wood-louse. The muscular foot extends the whole length of the under surface of the body ; the end of the snout is just visible ; there are no tentacles. A row of small gills is seen along each sido of the body under the edge of the mantle. A
. Natural history. Zoology. 6i6 AJOLLUSCA—APLACOPHORA. In some forms the animal is very long in the body and the shelly plates are placed at intervals. The animals, which are vegetable feeders, may be found clinging, lilce limpets, to the under surfaces of rocks and stones at low tide, and when detached will coil up much after the fashion of the well-known wood-louse. The muscular foot extends the whole length of the under surface of the body ; the end of the snout is just visible ; there are no tentacles. A row of small gills is seen along each sido of the body under the edge of the mantle. A remarkable feature in the shell of many chitons calls for speciil mention. The outer chitinoua layer of the valves is perforated for the passage of sense organs, which, in the family Chitonidse, are in part converted into eyes. The Polyplacophora are divided into families as follows, according to details of sculpturing, etc., of the valves:—Lbpidopleoriu^, Ischno- CHITO:<ID^, MOPALHD^, ACANTHOCIIITIDiE, CkYPIOPIACIU-S:, ChIIONID^. Order II.—Aplacophora, or Solenogastra. The Aplacophora, which are carnivorous, are so modified that they scarcely resemble molluscs at all. The body is worm-like and there is no trace of shell, but the much thickened outer skin contains shelly spicules, which probably represent the spines and scales of the Polyplacophora. The foot is extremely reduced, or altogether wanting. The gills are in a chamber at the latter end of the body, into which chamber also the excretory orifices open. Their blood is red. Two sub- orders are distinguished :— Sub-order —Nbomeniina, in which the foot is reduced to a ridge sunk in a groove along the ventral ^^- *• side of the body. (."chItodeema. The radula is of the usual many-toothed order, or wanting. There are four families :—^, Prokeomeniidje, Donuersiid^, and Parameniid^. Sub-order 2.—Ch^todermatina, represented by a single genua Chmto- derma, in which the body is extremely long
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