88 ARTHROPODA. 



GROUP C. MALACOSTRACA. Crustaceans with five cephalic, eight 

 thoracic, and six abdominal segments; a telson. 



Order 1. Arthrostmca (Edriophthalmata). Seven (rarely six) free 

 thoracic segments and sessile lateral eyes. No cephalothoracic [shield 

 or larval form. 



Amphipoda, body laterally compressed; gills on the thoracic 

 limbs. Gammarus pulex. Talitrus locusta, sand-hopper. Phro- 

 nima. Caprella linearis. Cyanms ceti. 



I s o p o d a, with vertically flattened body and gill-bearing abdom- 

 inal appendages. Asellus aquaticus, Oniscus murarius, wood-louse, 

 Armadillo vulgaris ; Tanais dubius, with two kinds of male. 



Order 2. Thoracostraca. A cephalothoracic shield and compound eyes 

 which are generally stalked. 



Cumacea, 4-5 free thoracic segments, two pairs of foot-jaws, no 

 abdominal appendages in the female, sessile eyes. Cuma. 



S t o m a t o p o d a, short cephalothoracic shield, five pairs of foot-jaws, 

 gills abdominal. Squilla mantis, locust-crab. 



S c h i z o p o d a, a large cephalothoracic shield, and eight pairs of 

 biramous thoracic appendages. Mysis, opossum-shrimp, with otocysts 

 in the tail-flaps. 



D e c a p o d a, large cephalothoracic shield. Thoracic appendages con- 

 sist of three pairs of foot-jaws, and five pairs of uniramous leet: (a) 

 Macrura with long abdomen; Palaemon, prawn, Crangon vulgaris, 

 shrimp, Astacus fluviatilis, cray-fish, Homarus vulgaris, lobster, 

 Palinurus vulgaris, rock-lobster, Nephrops Norvegicus, Norway 

 lobster, Pagurus Bernhardus, hermit-crab : (6) Brachyura with short 

 abdomen ; Cancer pagurus, edible crab, Carcinus mcenas, shore-crab. 



