Classes of Crustaceans. 1 07 



comprising all these forms the name Cirripedia, or 

 bristle-footed, has been given. 



Recapitulation. We have thus seen that the 

 seven classes of water-breathing, many-jointed forms 

 which make up the class Crustacea are very dissimilar 

 in details. They may be arranged in a tabular series 

 as follows : 



A. Sessile Crustaceans, often pseudo-parasitic, usually 



enclosed in a many valved shell = Sub-class I. 

 Cirripedia. 



B. Free, with a cephalo-thorax and two pairs of tho- 



racic limbs, none of the feet bearing gills = 

 Sub-class II. Copepoda (fig. 58). 



C. Free, with the body enclosed in a bivalve shell 



made of the extended dorsal integument ~ 

 Sub-class III. Ostracoda. 



D. Free, with no enclosing shell, feet gill-bearing, 



segments less or more than twenty = Sub-class 

 IV. Branchiopoda. 



E. Free, with a large cephalo-thorax, small walking 



limbs, six pairs of which are arranged around the 

 mouth = Sub-class V. Pcecilopoda. King Crabs. 



F. Free, with a cephalo-thorax, stalked eyes and a 



body of twenty segments = Sub-class VI. 



Podophthalmia. 



A. Thoracic limbs masticatory, ten abdominal 



limbs alone fitted for walking = Order I. 



Decapoda. 



a. With a long post-abdomen : Lobsters = 



Sub-order I. Macrura. 



b. With a soft limbless post-abdomen : 



Hermit Crabs = Sub-order II. Ano- 

 mura. 



