ARTHROPODA 285 



"whicli they live. The eggs require for their developement a 

 current of water, which is produced by the action of the 

 abdominal swimming-feet of the parent. The group is ex- 

 clusively marine ; the members of it inhabit shallow water, 

 and either live in crevices in coral rock, or burrow in the sand. 

 They often rest in the mouths of their burrows with nothing 

 but their eyes exposed above the sand ; in this way they lie 

 in wait for their prey, which they seize with astonishing 

 rapidity by means of their powerful subchelate maxillipedes. 

 They are extremely active in their movements, and difficult to 

 catch, retiring to the inner end of their burrows at the slightest 

 alarm. 



Sub-order 3. SCHIZOPODA. 



Chaeacteeistics. — Brazil Thoracostraca ; the carapace is large 

 and soft, the eight thoracic limbs are hiramous. Those modi- 

 fied to form, maxillipedes do Tiot differ Tnarhedly from the 

 others. Tlie eyes are stalked. 



The Schizopoda retain throughout their life a condition 

 which resembles that of the last of the series of larval forms 

 which take part in the metamorphosis of some macrurous 

 Decapods. This larva is known as the Mysis stage, and is 

 called after the opossum- shrimp, one of the best-known 

 Schizopods. 



The members of this sub-order differ markedly from the 

 Stomatopoda, in which group the maxillipedes attain the greatest 

 importance, for in the Schizopods each of the eight pairs of 

 thoracic appendages are biramous legs, none of them being 

 modified to form maxillipedes, although the two anterior pairs 

 may tend in a slight degree to resemble the mouth appendages. 

 The first antennae are biramous, and in the male are provided 

 with a curious comb-like structure covered with olfactory hairs. 

 The second antennae, a pair of mandibles, and two pairs of 

 maxillae complete the appendages of the head. 



The carapace is large, and attached to the body only by a 

 narrow area of fusion in the dorsal middle line ; in some forms, 

 as Siriella, it leaves most of the thoracic segments uncovered. 



The abdomen consists of six segments and a telson ; the 

 first five abdominal appendages in the female are usually small, 



