( 5 ) 



nera are most of them too large : thus, under Ligia he includes Phihseia 

 mmcarum (figured as Ligia melanocephala, a more natural alliance, by the 

 way, than M. Edwards, of Oniscus). Itea includes Itea proper and 

 Platyarthus (Br.)f and probably a third form. He has changed Brandt's 

 name, Ligidium, for Zia, and his Armadillo into Pentheus, whilst Arma- 

 dillium {Br.) figures here as Armadillo, Latr. The other genera described 

 by him are Phterusa, Oniscus, and Porcellio, the two latter including 

 as species many which can scarcely be looked on as even varieties. 



On Classification. 



Brandt, taking as familiar characters the number of joints in the termi- 

 nal appendages of the antennae and the number of pairs of caudal append- 

 ages (L e. the last pair of false feet), has divided the genera known to 

 him into two sections, viz., Ligiea (Ligia and Ligidium) and Oniscinea, 

 subdivided according to the length, form, and insertion of the exterior 

 caudal appendages, into (1) Porcellionea (Trichoniscus, Platyarthus, 

 Porcellio, Philoscia) ; and (2) Armadillinea (ArmadiUidium, Cubaris, 

 Armadillo, and Diploexochus). 



Although these generic groups are natural enough, he appears to 

 have mistaken the true nature of the caudal appendages, which in all 

 the genera belonging to this group consists truly of two pairs, as we 

 hope to show when we come to treat more in detail of them, although 

 in all the groups except Ligiea their true nature is somewhat obscured 

 by the truncation of the margin of the peduncle. In Ligidium, included 

 by him among the Ligiea, but which, as will be seen, we propose to 

 place in a separate division, the appendages are really two pairs. 



His lesser divisions and species are many of them faulty, being 

 governed nearly entirely by considerations of number and colour, charac- 

 ters of a very minor importance in classification, though oftentimes con- 

 venient when conjoined with the more permanent characters, of form, 

 position, and structure. Some of his genera probably must fall, at least 

 in their present shape, their descriptions being so imperfect as to render 

 them unrecognisable, owing to his imperfect means of observation : thus, 

 Trichoniscus may possibly turn out to be Itea, Zia, or some of their allied 

 genera, more fully described by later writers. 



Milne-Edwards has for the most part copied Brandt, but has pro- 

 posed new primary divisions, in the naming of which he has been sin- 

 gularly infelicitous. He has drawn his familiar characters from the 

 comparative length or brevity of the last false feet, as compared with 

 the terminal segment of the abdomen, and thus makes two primary 

 groups, Cloportidea maritiniea (Ligia and Ligidium) : and Clop&rtides 

 Urrestres, subdivided, according to the form and length of the last pairs 

 of false feet and their appendages, intoPorcellioniens ^Oniscus, Philoscia, 

 Deto, Porcellio, Trichoniscus, Platyarthus), Armadilliens (ArmadiUi- 

 dium, Armadillo (includes Cubaris), Diploexochus), and Tylosiens 

 (Tylus). 



The names of his primary divisions show us the danger of naming 

 groups from habits. Ligidium, although included among the Maritime 



