11 GENERA OF PHYLLOPODA 35 
carapaces, closely resembling those of the modern Estheria, are 
known in beds of all ages from the Devonian period to recent 
times; these carapaces are in several cases associated with fossils 
of an apparently marine type. None of the fossil species differ 
in any important characters from those now living, so that the 
Phyllopoda have existed in practically their present form for 
an enormously long period; this fact, and the evidence that — 
species of existing genera were at one time marine, explain the 
wide distribution of animals at present restricted to a remarkably 
limited range of environmental conditions. 
Summary of the Characters of the Genera. 
Sus-OrpEer PuHyLiopopa.—Branchiopoda with an elongated body, pro- 
vided with at least ten pairs of post-cephalic limbs, the heart extending 
through four or more thoracic segments, and having at least four pairs of ostia. 
Fam. 1. Branchipodidae.!—Carapace rudimentary, eyes stalked.; the 
second antennae flat and unjointed in the female, jointed and prehensile in 
the male; female generative opening single ; telson not laterally compressed, 
bearing two flattened lobes, or none. The heart extending through the 
thorax and the greater part of the abdomen. 
A, Eleven pairs of praegenital ambulatory limbs. 
a. Abdomen of six well-formed segments and a telson; anal lobes 
well formed, their margins setose. 
Branchinecta, Verrill—Second antennae of ¢ without lateral 
appendages ; ovisac of ? elongated. b. paludosa, O. F. 
Miull.—Cireumpolar. 
Branehiopodopsis, G. O. Sars?—Second antennae of g as in 
Branchinecta ; ovisac of 2 short. B. hodgsoni, G. O. Sars 
—Cape of Good Hope. 
Branchipus, Schaeffer—Second antennae of 3 with simple 
internal filamentous appendage. 6. stagnalis, Linn. — 
Central Europe. 
Streptocephalus, Baird—Second antennae of ¢ 3-jointed, the 
last joint bifid; an external filamentous appendage.  S. 
torvicornis, Wagn., Poland. 
Chirocephalus, Prévost—Second antennae of 3 3-jointed, with a 
jointed internal appendage, which bears secondary processes, 
four cylindrical and one lamellar. C. diaphanus, Prévost 
(Fig. 2, p. 20).—Britain, Central Europe. 
b. Abdominal segments five or fewer, and a telson. Anal lobes 
small or 0, sparsely or not at all setose. 
Artemia, Leach—Second antennae of ¢ without filamentous 
1 Consult’ Baird, ‘‘ Monograph of the Branchiopodidae,” Proc. Zool. Soc. 1852, 
p. 18. Packard, 12th Ann. Rep. U.S. Geol. Survey, part i., SAO 
2 Arch. f. Math. og Naturvidensk. xx., 1898, Nos. 4 and 6. Thiele, Zool. Jahrb. 
System. xiii., 1900, p. 563. 
