It is now understood that they are Euthyneurous Gastropods adapted to natatory locomotion and pelagic life.
In this family a great number of natatory vesicles are connected with the terminal arial vesicle, as in Fig. 101, Praya diphys.
The eyes were probably stalked, the antennae and mandibles biramous and natatory, and both armed with masticatory processes.
They have four short legs, of which the hinder have toes, united by a natatory membrane, and only three claws to each foot.
The stout endopodites, on the other hand, probably performed the double function of natatory and ambulatory legs.
Its exact position likewise varies, for it arises either between the first or second pairs of natatory legs.
And yet 'this natatory art' is but little cultivated amongst us.
In this fig. 3, it may be observed that the natatory legs and caudal appendages of the pupa have not as yet been moulted.
Confident in his natatory powers, he had at first believed this feat to be not only possible, but probable and easy.
Many female parasitic crustaceans have lost their natatory legs.