Lepidurus, Leach—Telson produced backwards to form a plate above the anus; endites of first thoracic limb short. L. productus, Bosc.—Central Europe. L. viridis, Southern Australia, New Zealand, L. patagonicus, Bergh, Argentines.
Fam. 3. Limnadiidae.—Body compressed; carapace in the form of a bivalve shell, the two halves capable of adduction by means of a strong transverse muscle; second antennae biramous, alike in both sexes; in the male, the first or the first and second thoracic limbs prehensile; telson laterally compressed.
A. Only the first thoracic limbs prehensile in the male; the carapace spheroidal, without lines of growth; head not included within the carapace-chamber.
Limnetis, Lovén—Compound eyes fused; anal spines absent; ambulatory limbs 10–12. L. brachyura, O. F. Müll (Fig. [3], p. 21).—Norway, Central Europe.
B. The first and second thoracic limbs prehensile in the male; carapace distinctly bivalve, enclosing the head, with concentric lines of growth round a more or less prominent umbo.
Eulimnadia, Packard—Carapace narrowly ovate, with few (4–5) lines of growth. E. mauritani, Guérin—Mauritius. E. texana, Packard—Texas, Kansas.
Limnadia, Brongniart—Carapace broadly ovate, with numerous lines of growth, without distinct umbones; L. lenticularis, Linn.—Northern and Central Europe.
Estheria, Rüppell—Carapace with well-marked umbones and numerous lines of growth, oval; E. tetraceros, Kryneki—Central Europe.
Leptestheria,[[29]] G. O. Sars—Carapace compressed, oblong. Rostrum with a movable spine; thoracic limbs with accessory lappet on the exopodite. L. siliqua, G. O. Sars—Cape Town.
Cyclestheria,[[30]] G. O. Sars. C. hislopi, Baird—Queensland, India, East Africa, Brazil.