268 PROCEEDINGS OF SOCIETIES. 



can learn, multi-articulate. Examples — Ligia, Ligidium, Titanethes, 

 Styloniscus. 



2nd. The articulations elongated, somewhat flattened, and gene- 

 rally covered with hair, few in number, gradually tapering, but not 

 subulate, the terminal one terminating in a narrow articulated hair. 

 Examples — Oniscus, Porcellio, Philoscia (?), Armadillium, Armadillo, 

 Spherillo, Tylus, Scyphax, Platyarthus (?), Deto (?). 



The characters of the second articulation of the peduncle, as hinted 

 above, divide these into two groups. 



3rd. The articulations few in number, the whole filament gradu- 

 ally tapering, subulate, and perfectly naked, terminating in a tapering 

 filament. Examples — Philougria, Itea, Trichoniscus (?). 



In all these genera the number of joints in the antenna? has been 

 used as a generic character by Brandt, &c, except Ligia, Ligidium, and 

 Platyarthus ; but in grouping the genera no regard has been, as far as I 

 know, paid to the far more important character — that of the form of 

 the tige. 



Dana states that number of articulations of the tige is of no value as 

 a character, and instances as a proof it the genus Scyphax, in which he 

 states that in the young the tige has its apex with the rings half marked. 

 From the character of the figure it is apparent the drawing was made 

 from a dead specimen, probably a dried one, in which, owing to the 

 contraction of the tissues, circular cracks had taken place, a fact which 

 any microscopist who examines the antennae of many of the Cloportides 

 under the glass must be fully aware of. The specimen also which he 

 figures as the young of Scyphax, judging from its tail appendage, can 

 scarcely belong to that genus at all ; at least, though I have carefully 

 examined the young of all our native genera, most of them recently 

 hatched, yet I never met an instance in which the tail appendages dif- 

 fered much from that of the full-grown animal : but we will speak of 

 this anon in our enumeration of genera. 



There is one objection which has been started to using the characters 

 of the tige as generic, which must be noticed, i. e. that in the young the 

 number of joints are less than in the adult This statement is only 

 partially true. Eor instance, in most of the genera in which the antenna? 

 are multi-articulate, the antenna? of the young and adult differ much; 

 but in those of the second and third types, given above, in some species 

 there is no difference at all, the articulations being all present, though 

 the terminal ones are much shorter than normal. This is the case, for 

 instance, in very young P.pruinosus and P. scaler, even when the coxa? 

 of the seventh cephalo- thoracic segments and the legs of the same pair 

 are absent : and even where it holds good there can be no mistake, for 

 other characters, such, for instance, as that noted above, the absence 

 of the seventh coxa?, at once marks the animal as immature ; hence I 

 think Dana is wrong in making sub-genera of Trichoniscus, Porcellio, 

 and Oniscus, merely because the number of joints in their antenna? have 

 been too much dwelt on. 



