294 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Reptantia. — Rostrum reduced or absent, depressed if 

 present. Body depressed. First abdominal 

 somite smaller than rest. Stylocerite absent. 

 Second antennal scale reduced or absent. In the 

 legs generally a basi-ischium, and two fixed 

 points in the carpo-propodal articulation. Male 

 genital opening coxal and sternal. Abdominal 

 limbs 1-5 reduced or absent, and not used for 

 swimming. 

 The four tribes belonging to the Reptantia are 

 divided into two groups. 



I. Third legs like the first. Abdomen macrarous. 

 Grnathobases of second maxillae narrow. Exopodites of 

 maxillipedes with lash directed forward. Grills numerous. 



(1) Palinura. — Carapace fused to epistoma. Rostrum 



small or absent. Inner lobes of second 

 maxillae and first maxillipedes reduced. Body 

 depressed. 



(2) Astacura. — Carapace free from the epistoma. 



Rostrum large. Inner lobes of second maxillae 

 and first maxillipedes not reduced. Body sub- 

 cylindrical. 



II. Third legs unlike the first, never chelate. Abdo- 

 men rarely macrurous. Grnathobases of second maxillae 

 broad. Exopodites of maxillipedes with lash directed 

 inward. Grills few. 



(3) Anomura. — Carapace not fused with epistoma. 



Last thoracic sternum free, its legs differing from 

 the others. Abdomen anomurous. Movable 

 antennal scale. Third maxillipedes narrow. 



(4) Brachyura. — Carapace fused with epistoma. Last 



thoracic sternum fused with rest, its legs like the 

 others. Abdomen brachyurous. No movable 

 antennal scale. Third maxillipedes broad. 



