STALK-EYED CRUSTACEA 391 



Section A. Porcellanodea. 



Porcellanodea . . Henderson. 

 PorceUa)iicns . . H. Milne Edwards, 

 Porcellanidea . . De Haan, Dana, Stimpson, Miers, 

 Haswell. 



Carapace broadly ovate, smooth, with the regions not 

 well marked ; the front usually trilobed, lobes never of 

 great length. First pair of legs broad and often flattened ; 

 the walking legs robust and of moderate length. 

 Antennules concealed ; the antennal peduncle directed 

 backwards. Eyes always pigmented, and partially con- 

 cealed in orbits. External maxillipedes with the third 

 joint broad, and the fourth joint provided with a 

 prominent internal lobe. Abdomen bent under the 

 thorax ; females with two (or three) pairs of slender 

 uniramous appendages on the fourth, fifth (and third) 

 segment ; males with a single genital pair on the second 

 segment. 



Range. — All seas between tide marks. As they are 

 usually found under stones, they may live also at great 

 depths, where they would be picked up with difficulty. 



One family. 



Family I. Porcellanidae. 



Porcellanidcc . . . Henderson. 

 Characters the same as the Section. 



Synopsis of the Genera. 



I. First joint of antennal peduncle short, not reaching 

 the superior margin of the carapace. 



a. Carapace subovate ; frontal region triangular, with 

 more or less undulating margin. — {PetrolistJies^ 



