114 STALK-EYED CRUSTACEA 



retractile within the postforaminal portion of the orbits, 

 which is very deep. The internal antenna; are always 

 lodged in fossae under the front. The basal articulation 

 of the external antenna; always separates the antennulary 

 fossae from the orbits ; sometimes free, sometimes soldered 

 to the test. The antennary region is not as great as the 

 buccal cavity. The epistome is very short, much wider 

 than long. The buccal cavity is very wide in front, and 

 long from before backwards. 



The genital orifices of the male, the efferent canals of 

 the respiratory regions, and the gills are arranged as in 

 the Oxyrhynclia. 



Legion Cancrinea. 



Caiicrinea, or Canci'oidea typica . Dana, Miers. 



The carapace is not antero-laterally convex, and 

 largely developed so as to form a vaulted respiratory 

 chamber. The buccal cavity is usually well defined. 

 The flagella of the antennae are not elongated. The 

 last joint of the walking legs is styliform and unarmed, 

 or in the fifth pair expanded into an ovate swimming 

 organ. 



Family I. Cancridae. 

 Family II. Portunidae. 



Synopsis of the Families. 



A. The last joint of all the walking legs is the same 

 shape. — ( Cancridtv. ) 



B. The last joint of the last pair of walking legs does 

 not resemble that of the others in shape, being flattened, 

 expanded, and used for swimming. — {Portunidcu.) 



