210 



Arthropoda. Class 1. Crustacea- 



is provided with a pair of caudal appendages at the tip ; the abdominal appen- 

 dages (six pairs) are, however, like those of the Malacostraca. A large part of the 

 body with the limbs (not the thorax alone, as in the Malacostraca), is covered 



rig. 171. Nebalia Geoffrayi. VIII Eighth thoracic segment, 1, 7 first and seventh 

 abdominal segment; J, — A^ first and second antennae, Chead; S^ Hj first and sixth 

 abdominal appendages ; K^, Kg first and eighth thoracic appendages ; o eye, p mandibular 

 palp, r caudal appendage, S carapace (left-side removed). — After H. Milne-Edwards. 



by a large, compressed carapace, which lies loosely over the thorax, without 

 undergoing concrescence with it. On the whole, the animal exhibits a curious 

 combination of the characters of the PhyUopoda and the Malacostraca. 



Synopsis op Ordees. 



Stalked eyes. 



Carapace present, usually well- 

 developed. 

 Second antenna with, exopod. 



Sessile eyes. 



Carapace small or absent. 



Second antenna witliout exopod. 



/ 6. Decapoda \ 



I 7. ~ 



Stomatopoda > No brood-pouch. 



1. Euphausiaceaj 



2. Mysidacea. \ Brood-pouch 



3. Cumacea f present. 



4. Isopoda j One pair of 



5. Amphipoda / maxillipeds. 



Order 1. Euphausiacea. 



The Euphausiacea are transparent, prawn-like animals, a 

 few c/m. long, which live in great numbers in the open sea. They 

 differ from all Malacostraca in that none of the thoracic 

 feet are modified as maxillipeds, but all the eight pairs, 

 though the last two may be degenerate, are essentially alike, and all 



