PACKARD.] PHYLLOPODS OF NORTH AMERICA. 297 
his order Phyllopoda into two suborders, Cladocera and Branchiopoda. 
Gerstaecker in Bronn’s Classen und Ordnungen Arthropoden, 1866~79, 
adopts the order Branchiopoda, and divides it into three suborders, Os- 
tracodea, Branchiopoda genuina, comprising the Cladocera, Phyllopoda 
of other authors, and the Branchiura (Argulus, &e.). 
In 1879 the writer, in his ‘“‘ Zoology for Colleges,” adopted the order 
Branchiopoda, with three suborders, viz, Ostracoda, Cladocera, and Phyl- 
lopoda. 
Suborder PHYLLOPODA. 
In this group the body is usually (the Branchipodide excepted) in 
part covered by a large carapace (the mandibular segment greatly de- 
veloped tergally), which is in the lower forms (Limnadiacea) bent down, 
forming two valves, connected by a true hinge, and opening and shutting 
by an adductor muscle, so that the shell resembles that of a bivalve 
molluse, such as the fresh-water Cyclas and Pisidiwm. They have two 
pairs of antenne, a pair of mandibles, and two pairs of maxille, and 
in Apodide a pair of maxillipedes. The name of the group, Phyllopoda, 
is applied to them on account of the feet, which are broad and leaf-like, 
with a series of six primary inner lobes or endites and two exites, the latter 
forming a gill and accessory gill or fabellum. 'Theabdomen is not clearly 
differentiated from the thorax, and the abdominal feet are not different 
in shape from the thoracic appendages. The number of body-segments 
varies more than in any other group of genuine Crustacea, there being 
seventeen in Limnetis and sixty-nine in Apus, or over three times as 
many as in the lobster or Decapods in general; the segments are thus 
often irrelatiyely repeated, a sign of inferiority. The. eyes are either 
sessile and united into a single mass, or, in the highest family (Branchi- 
podide), they become stalked, thus anticipating the stalked eyes of the 
Decapoda. The telson is usually large and spiny, bearing in all the 
genera a pair of caudal appendages probably homologous with the hmbs. 
All the members of the suborder hatch from the egg in the Nauplius 
form, like that of the Copepod Crustacea, with some differences, all 
having three pairs of appendages corresponding to the two pairs of 
antenne and mandibles of the adult. 
The species for the most part live in pools of fresh water liable to 
dry up in summer; those of Artemia live in brine pools and lakes. The 
eggs, after being fertilized and borne about for a time under the shell 
or in egg-sacs, are finally suffered to drop to the bottom of the pond; 
here they lie after the water of the pond has evaporated, the eggs re. 
maining in tae dry mud until, the ponds having been refilled by the 
autumn rains, the young hatch out and the cycle of life begins anew. 
Family I. LIMNADIADZ Baird. 
Limnadiade Baird, Proc. Zool. Soc. London, XVII, 86, 1849; Ann. & Mag. Nat. Hist. 
2d Ser. XIV, 229, 1854. 
Estheriade Packard, Hayden’s U. 8. Geol. Surv. Ter., for 1873, 618. 1874. 
Body inclosed in a bivalved shell; head usually with a large ros- 
trum; eyes compressed, small, sessile, closely contiguous or united. 1st 
antenni minute, 3 jointed or "multiarticulate, the ‘segments not being 
well marked; 2d antennz large, with two flagella, each consisting of 
from 9 to 20 joints. A pair of mandibles; one or two pairs of maxillee ; 
10 to 27 pairs of swimming phyllopod feet, each with six lobular endites, 
and a gill and flabellum divided into two ‘divisions, the upper in the fe- 
