36 CRUSTACEA BRANCHIOPODA CHAP. 



appendage, 2-jointed, the second joint lamellar. A. salina, 

 Linn. Brine pools of the Palaearctic region. 



c. Hinder abdominal segments united with telson to form a fin ; anal 

 lobes absent. 



Thamnocephalus, Packard Head with a branched median pro- 

 cess of unknown nature. Only species T. platyurus, Packard 

 Kansas, U.S.A. 

 B. Nineteen pairs of praegenital ambulatory limbs. 



Polyartemia, Fischer Second antennae of < forcipate ; ovisac 



of $ very short. Only species P. forcipata, Fisch. 



Fam. 2. Apodidae. 1 Carapace well developed as a depressed shield, 

 covering at least half the body. Eyes sessile, covered ; no male clasping 

 organs ; anal lobes long, jointed cirri. 



Apus, Scopoli Telson not produced backwards over the anus ; 

 endites of first thoracic limb very long. A. cancriformis, 

 Schaeffer Britain, Europe, Algiers, Tunis. A. australiensis, 

 Central Australia. 



Lepidurus, Leach Telson produced backwards to form a plate 



above the anus ; endites of first thoracic limb short. L. pro- 



ductus, 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, Loven Compound eyes fused ; anal spines absent ; 



ambulatory limbs 10-12. L. bracKyura, 0. F. Mull (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, Guerin 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, Rlippell Carapace with well-marked umbones and 



numerous lines of growth, oval ; E. tetraceros, Kryneki 



Central Europe. 

 Leptestheria, 2 G. O. Sars Carapace compressed, oblong. Ros- 



1 Bernard, loc. cit. p. 19 ; Baird, Proc. Zool. Soc. 1852, p. 1 ; Sayce, Proc. Roy* 

 Soc. Victoria, xv., 1903, p. 224. 



2 Sars, Arch. f. Math, og Naturvidensk. xx., 1898, Nos. 4 and 6. 



