376 CRUSTACEA ENTOMOSTRACA. 



of the 9th and 10th pairs of legs (Esther ia), or in box-like brood 

 pouches borne on the llth pair of thoracic appendages, at the 

 base of which the oviducts terminate. These are formed by 

 the apposition of the flabellum and a rounded concave plate pro- 

 jecting from the distal portion of the limb (Apus). 



In the eggs of Branchipus the segmentation is complete at 

 any rate in the early stages. The nauplius larva is charac- 

 terized by several peculiarities. Its body is, in Branchipus and 

 Estheria, distinctly divided into a cephalic and post-cephalic 

 region ; the upper lip is extraordinarily large ; the first pair of 

 antennae is usually rudimentary and sometimes even absent, 

 while the second pair is exceptionally large (Balfour). 



Almost all the Phyllopoda belong to inland waters, and 

 principally inhabit shallow fresh- water pools. When the latter 

 dry up the eggs lying in the dry mud may retain their power of 

 development for years. 



Tribe 1. ANOSTRACA. 



Body cylindrical, without carapace ; eyes pedunculated ; second 

 antennae prehensile in the male ; 11-19 pairs of thoracic legs bearing 

 two or three exites ; small paired copulatory appendages in the male ; 

 the female carries the eggs in a ventral egg sac in which the oviducts 

 terminate. Widely distributed in fresh and salt water lakes. 



Fam. 1. Branchipodidae. Abdomen distinctly segmented in both sexes, 

 with paired caudal appendages ; prehensile antennae of male distinctly 

 jointed ; 11 pairs of thoracic legs, usually with 2 exites (3 in Chirocephalus). 

 Artemia ~Leach, in salt water lakes * ; ArtemiopsisG.O. Sars ; Branchinecta 

 Verrill ; Branchipus Schaff (Fig. 247) ; Chirocephalus Prev. occurs in 

 Britain ; Branchipodopsis G.O.S. ; Branchiopsilus G.O.S. 



Fam. 2. Thamnoeephalidae. Abdomen terminates in a broad swim- 

 ming plate. Thamnocephalus Packard, N. America. 



Fam. 3. Polyartemiidae. Abdomen of female imperfectly segmented ; 

 prehensile antennae of male not jointed ; 19 pairs of thoracic appendages, 

 with three exites. Polyartemia Fischer, with vestigial mandibular palp 

 in P. forcipata. Tundras of N. Europe and Asia and Alaska. 



Tribe 2. NOTOSTRACA. 



Shell shield-shaped fused in front with the head shield ; lateral eyes 



* It has been stated that it is possible, by diminishing the salinity of 

 the water inhabited by a colony of Artemia salina to induce changes in 

 their characters so that they assume those of the genus Branchipus. The 

 evidence in support of this statement has however been shown to be 

 quite insufficient. Cf. Bateson, Materials for the Study of Variation, 

 p. 96 ; Grochowski M. Ueber eine neue im Siisswasser lebende Species 

 von Artemia, Verh. Zool. Bot. Ges., Wien, 1895, p. 95. See also Samter 

 and Heymons, Variationen bei Artemia salina, Abh. AJcad. Berlin, 1902, 

 Anh. 2. 



