INVERTEBRATE ZOOLOGY. 31 



Legion 1. Phyllocarida {Leptostraka). . . .This group, mostly fossil, contains 



but a single pelagic form, valuable as a 

 link between Entomostraka ancl Malakos- 

 traka. A small integumental duplicatnre 

 covers the head and thorax. The abdonien 

 is 8-jointed, thus departing fi-om the con- 

 stant number found in Malacostraka. 

 The feet are like those of Phyllopods. 

 i^ Nebalia. 



Legion 2. Arthrostraka (Edriophthalmata) Sessile-eyed Malacostraka, 



with free thoracic segments, and without 

 carapace. Thoracic appendages distribu- 

 ted as one maxilliped and seven legs. 

 Brood cavity borne between thoracic legs. 



Order 1. Amphipoda Compressed forms, body generally bent 



into a curve. Grills upon the thoracic 

 legs. Abdomen with six pairs of legs, of 

 which the first three are used in swim- 

 ming, and the last three form a springing 

 organ. In a few forms the abdomen is 

 reduced. -^ Gauimariis. 



Order 2. Isopoda Depressed forms with seven free thoracic 



segments. The abdominal appendages 

 are in the form of flattened plates and 

 protect the gills. -^ Porcellio. 



Legion '6. Thoracostraka (Podophthalmata). . . .Eyes situated upon moval)le 



stalks. Carapace involving all or nearly 

 all the thoracic rings. Brood cavity ufjon 

 the ventral side of the flexible abdomen 

 and protected by the sixth abdominal ap- 

 pendage and the terminal segment 

 (telson). 



Order 1. Cumacea Carapace small, involving only 8-4 tho- 

 racic segments, two pairs of maxillipeds 

 and six pairs of legs. Abdomen of fe- 

 male without appendages ; of male vnth 

 3-0. -^ Diastylis. 



