308 PHYLUM ARTHROPODA. 
Series IJ. Eumalacostraca. 
Division 1. Syncarida, the order Anaspidacea, primitive fresh-water 
forms, without a carapace; with the eight thoracic segments all 
distinct (Azzasfzdes), or with the first one fixed to the head (Koonunga) ; 
with stalked eyes in Anaspides, sessile eyes in Koonunga; with 
lamellar branchize on the thoracic legs, whose slender exopodites are 
also respiratory. 
Division 2. Peracarida, with a carapace that leaves at least four of 
the thoracic segments free, with the first thoracic segment always fused 
to the head, with usually sessile eyes, with a brood-pouch on the 
thoracic appendages of the female, with an elongated heart, with 
direct development. Numerous orders including :—the pelagic Mysi- 
dacea (formerly united with Euphausiacea 
as Schizopods), e.g. dZysis; the pelagic 
and deep-water Cumacea, e.g. Cuma and 
Diastylzs ; the Isopods, with dorso-ventral 
flattening of the body, a posterior heart, 
and respiratory organs on the abdominal 
limbs, ¢.g. the terrestrial wood-lice (Por- 
cellio, Oniscus, etc.), which show minute 
trachea-like respiratory tubes in the abdom- 
inal limbs, and corresponding forms on the 
shore (e.g. Ligza, Jdotea) ; the Amphipods, 
with lateral flattening of the body, an 
anterior heart, and respiratory organs 
usually on the thoracic limbs, e.g. Gam- 
marus locusta in the shore pools, G. pulex 
in fresh water, and sandhoppers like 
Talitrus and Orchestia; the ‘‘no body” 
crabs, Caprella; Phronima, living inside 
the glassy case of the free-swimming 
Tunicate Pyrosoma. 
: : Division 3. Hoplocarida, with a carapace 
Fic. 162.—An Amphipod that leaves et feast four of the thoracie 
(Caprella linearis), segments free, with stalked eyes, with the 
The two anterior thoracic seg- eggs carried in a chamber formed by the 
Be dan we cee maxillipedes, with an elongated heart, 
duced and without append- 2nd with a complicated metamorphosis. 
ages; the fourth and fifth Order :—Stomatopods, e.g. Sguzl/a, with 
thoracic segments bear only the second maxillipedes forming very large 
respiratory plates. raptorial organs. 
Division 4. Eucarida, with a cephalo-thoracic shield uniting the 
head and thorax segments; with stalked eyes; with a saccular heart ; 
with eggs attached to the abdominal endopodites; with spherical 
spermatozoa showing peculiar radiating pseudopodia; usually with a 
complex metamorphosis. 
Order 1. Euphausiacea :—shrimp-like surface and deep-water forms, 
with biramous thoracic limbs as in Mysids, e.g. Huphausza. 
Order 2. Decapoda:—with the three anterior thoracic limbs 
turned forward as maxillipedes, with the other thoracic limbs almost 
always uniramous, ; 
