//. TYPES IN DETAIL IVITH THEIR SUBORDINATE GROUPS. 25 



flattened plates and protect the 

 gills, which are placed upon 

 them. Some are reduced, parasitic 

 forms. 



X Asellus, Porcellio. 



Super-order 3. THORAKOSTRAKA . . Eyes situated upon movable 



stalks. Carapace involving all or 

 nearly all the thoracic rings. 

 Brood cavity upon the ventral 

 side of the flexible abdomen and 

 protected by the sixth abdominal 

 appendage and the terminal seg- 

 ment (telson). 



Order i . Cumacea Carapace small, involving only 3-4 



thoracic somites, two pairs of 

 maxillipeds, and six pairs of legs. 

 Abdomen of female without ap- 

 pendages; of male with 3-2. 



X Diastylis. 



Order 2. Stomatopoda Carapace involving five thoracic 



somites, five pairs of maxillipeds, 

 and three pairs of legs. Gills upon 

 the abdominal appendages. 



X Squilla. 



Order 3. Schizopoda Carapace involving entire thorax, 



eight pairs of two-branched, gill- 

 bearing, thoracic legs. No maxil- 

 lipeds. 



X Mysis. 



Order 4. Dekapoda Carapace large and heavy, involv- 

 ing the entire thorax, three pairs 

 of maxillipeds, and five pairs of 

 legs, of which the first bears 

 heavy claws. Gills at base of 

 thoracic feet upon the sides, pro- 

 tected by the edge of the carapace. 

 X Homarus, Cancer. 



