550 PHILOSOPHY ,Or ZOOLOGY. 



E. Abdomen of both sexes four johiied. Two anterior 

 legs dldactyle. 



36. Leucosia. 37. Ebalia. 38. Ixa. 



B. Macuoura Tail about the length of the body, and 

 not concealed under the shield. 



The animals of this group differ from those of the pre- 

 ceding, in the produced form of their bodies. In the former, 

 the breadth of the body usually equals or exceeds the 

 length, while in these the length greatly exceeds the 

 breadth. Dr Leach distributes the genera in the follow- 

 ing manner : 



A. Tail on each side zvith simple appendices. Legs ten ; 

 anterior pair largest and dactyle. 



1. Pagurus. S. BiReus. 



B, Tail on each side zaith foliaceous appendages, form- 

 ing zvith the middle tail process a fan-like fn. 



a. Interior antenna zvith very long footstalks. 

 Division I. External antennae squamiform. Legs ten, 



alike and simple. 



3. SCYLLARUS. 4. ThENUS. 



Division II. External antennas setaceous, and very 

 long. Legs ten, alike and simple. 



5. Palinurus. 



Division III. External antennae very long and seta- 

 ceous. Legs ten, anterior pair didactyle, fifth pair spu- 

 rious. 



6. PORCELLARIA. 7. GaLATEA, 



b. Interior antenntE zvith moderate peduncles. 



Division I. Exterior lamella of the tail simple. An- 

 tennas inserted in the same horizontal line, the interior ones 

 with two setae, the exterior ones simple. Legs ten. 



8. Gebea. 9. Callianassa. 10. Axius. 



