BBITISH ASSOCIATION. 267 



4. The superior margin as in No. 3, but not rising above inferior bor- 

 der of orbits — Ligia, Ligidium (?). 



There may be, and probably are, two other types at least, viz., that 

 of Scyphax, and Titanethes, but I have only seen figures of these, the 

 latter is described as having large lateral, but no median lobes. 



These naturally lead us to consider the characters of the antenna? ; 

 and here we are dealing with organs whose importance has been to a 

 certain extent recognised, though apparently neither has their full nor true 

 bearing on classification been hitherto considered. The number of joints 

 without any reference to the more important character of form, has been 

 too much relied on, and hence some most incongruous groupings, as of 

 Philoscia and Oniscus, have been made ; but of this more anon : first, 

 to consider their general structure : — 



III. The Characters of the Antennae. 



First, of the Internal antennae. — These are merely rudimentary 

 through the entire group, generally consisting of but three short articu- 

 lations (Porcellio has four), and seldom passing beyond the front. They 

 are inserted internal to, and at the base of, the external antennas ; they 

 afford but little assistance in classification ■, for although jthey have 

 been made use of to distinguish genera, in the higher divisions they 

 are useless as diagnostic characters. "We pass then to the next 

 or — 



External antennae. — These are invariably simple, being made up of 

 a peduncle, which is pretty constant in its characters, and a filament or 

 tige, which varies much, and therefore affords good classificatory cha- 

 racters. The peduncle invariably, as far as we know, consists of five 

 joints: in some, as Ligia, a sixth appears to exist, but a little examina- 

 tion will show this to be a part of the third ring. The only joint which 

 affords any useful character is the second, which, in some genera, as 

 Armadillium, Porcellio, and Oniscus, is narrow at its articulation with 

 the first ring, and then suddenly swells out into a broad expanse, con- 

 tracting again slightly towards its articulation with the third joint; 

 while in others, as Philoscia, Ligia, Philougria, Itea, and Ligidium, 

 the second joint is globular : another argument for the separation of 

 Philoscia and Oniscus. The carvings and sulcationson the joints of the 

 peduncle, however, occasionally afford useful specific characters. 



From the extremity of the peduncle arises the filament, and of this, 

 trusting to form alone, the seven following types have been described. 

 This organ has attracted much attention ; but unfortunately, as I said 

 before, too much attention has been paid to mere number, and too little 

 to form. 



Eegarding form only, we find the filament constructed on three 

 types : — 



1st. The articulations are short, globular, cupped at their upper ex- 

 tremities, which are fringed with hairs, and receive the inferior portion of 

 the articulation next succeeding. These filaments are all, as far as I 



