. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 263 There is still another method of locomotion to be described. Solenomya is able to swim quite actively. It always swims with the anterior end of the shell pointed forward ^) and the movement consists of a series of short darts that remind one of the swimming of a squid. Each dart is accompanied by certain movements of the foot that are very misleading when considered by themselves. Not infrequently 2) it has been supposed that the swimming is accomplished by the energetic spreading of the muscular flaps accom- panied by th
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 263 There is still another method of locomotion to be described. Solenomya is able to swim quite actively. It always swims with the anterior end of the shell pointed forward ^) and the movement consists of a series of short darts that remind one of the swimming of a squid. Each dart is accompanied by certain movements of the foot that are very misleading when considered by themselves. Not infrequently 2) it has been supposed that the swimming is accomplished by the energetic spreading of the muscular flaps accom- panied by the retraction of the foot. That the animal is able to burrow its way through water much as it burrows through mud. Others have found that a strong stream of water is thrown from the mantle chamber through the small posterior opening at intervals corresponding to each forward dart, but the method of expelling the water seems never to have been understood. It will be ne- cessary to describe the structure of cer- tain parts in order to make the mechanics of swimrping clear. The shell is rather delicate and nearly cylindrical. The cuticle of the Fig. 8. Fig. 7. Solenomya velum, seen from the right side, with the foot protruded. / foot; TBS margin of the calcareous portion of the shell, seen through the rather trans- parent cuticle; yo posterior opening of the mantle chamber. In position this opening corresponds to the siphons, but it is a single opening. Notice the alternately thick and thin portions of the cuticle, radiating from the beaks to the free border. The thickened portions insure great elasticity, the thinner portions allow for the plaiting that takes place when the cuticle is folded into the mantle chamber. Fig. 8. Solenomya velum, seen from the ventral side, wilh the foot protruded. ao anterior opening of the mantle chamber; / foot; ms margin of the calcareous portion of the shell, seen through the rather transparent cuticle; po posterior opening of the mantle
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