THE ONISCID.E 427 



simplicity of this arrangement is ratlier rudely disturbed, 

 when it appears that PorcelUo has to be divided into seven 

 genera or sub-genera and Oniscus into five, and in fact with 

 one or two recent additions the Oniscidae contain twenty- 

 one genera instead of only six. Little more can be done 

 here than to mention their names. 



^ PorcelUo^ Latreille, 1804. In this genus, after restric- 

 tion, Budde-Lund describes seventy-one species, besides 

 giving the names of more than a score recorded without 

 description or imperfectly described. To this long list 

 additions have since been made, as lamellatus, Uljanin, 

 from the Mediterranean and the Azores ; cristatus, Dollfus, 

 from Surinam ; Marioni, Aubert and Dollfus, from Marseilles ; 

 ^rovincialis, Aubert and Dollfus, from Salon, in one of the 

 districts of Provence, the most arid and remote from human 

 habitations. Moreover, four or five new species from Syria, 

 chiefly collected by Dr. Th. Barrois, have been named by 

 M. Dollfus during the year 1892. Only the following 

 four species out of this extensive genus have been re- 

 corded in Great Britain. 1. — PorceUio scaher, Latreille, is 

 extremely common over the whole of northern and central 

 Europe and the North of America. It extends to Green- 

 land, and none of the land Isopoda range further to the 

 north than this does. It is said also to reach the Cape of 

 Good Hope and to have been found in Central America. 

 2. — PorceUio pidu^, Brandt, is perhaps the same as the 

 earlier PorceUio sinnico^mis, Say. It is distinguished by a 

 large apical tooth on the second joint of the second antennae, 

 and by the black and yellow markings of the pereeon. 

 Together with the preceding species it belongs to a section 

 of the genus in which the last segment is triangularly pro- 

 duced, with a sharp apex. 3. — PorceUio dilatatus, Brandt, 

 belongs to a section in which the last segment is produced 

 with a rounded apex. It does not appear to be at all 

 common in Great Britain. 4. — PorceUio Icevis, Latreille, 

 belongs to a group distinguished from that which includes 

 all the other three by having the hind margins of the first 

 three pera?on-segments less laterally sinuate, the side- 

 plates less, with the hinder angles in the earlier segments 



