MALACOSTRACA 391 



Its limbs (Fig. 222 E) are flat. Their endopodite is narrow and 

 possesses five indistinct joints. Sometimes the long basipodite 

 is divided and its distal region added to the endopodite as a 

 preischium (p. 336). The exopodite is broad and there is a very 

 large epipodite, which serves as a gill. (The related Paranebalia, 

 however, has a slender exopodite with a flagellum, and a small epipo- 

 dite.) The first four pairs of abdominal limbs are large and biramous, 

 the fifth and sixth small and uniramous. 



The alimentary canal possesses a proventriculus of relatively simple 

 type, several pairs of simple mid gut coeca, and an unpaired posterior 

 dorsal coecum. The heart is long, reaching from the head to the 4th 

 abdominal somite. The nervous system is of primitive type (p. 340). 

 The excretory organs have been alluded to on pp. 346, 348. 



The 2imTsi2\ feeds by straining particles from the water by means of 

 an elaborate arrangement of setae of different kinds on the thoracic 

 limbs, the necessary currents being set up by a pumping action of the 

 same limbs. These work upon a principle similar to that employed by 

 the Branchiopoda, the exopodites and epipodites acting as valves for 

 pumping chambers between the limbs, but it is the backward stroke 

 that enlarges the chambers, and they are closed by the forward flap- 

 ping of their valves. Development is direct, the embryos being carried 

 between the thoracic limbs of the mother, held in by the long setae 

 on the limbs, but not glued to them like the eggs of the crayfish. 



Subclass HOPLOCARIDA (STOMATOPODA) 



Malacostraca with a shallow carapace which is fused with three 

 thoracic somites and leaves four uncovered ; two free pseudosomites 

 on the head ; stalked eyes ; the first five thoracic limbs subchelate and 



Fig. 268. A male Squilla fna?itis. From Caiman, a.' antennule; a." antenna; 

 p. penis; sc. scale (exopodite) of antenna ; th.\ thr, th}, first, second, and last 

 thoracic limbs. 



the last three biramous ; no oostegites ; a large abdomen whose first 

 five pairs of limbs bear gills on the exopodites, while the sixth forms 

 with the telson a tail fan; and a large, branched "liver". 



