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antennae lie buried within this sulcus, curled over between the lateral 

 lobes of the third and fourth, or cephalic, segments. 



We have then the following rings represented : the first antennary 

 (i. 0. second normal ring) ; the second antennary (third normal). As to 

 the first (or ophthalmic) ring, it scarcely seems to exist ; what I haTo 

 called the lobes of the superior ridge may represent it, but I think 

 rather they are the epimerals of the third ring. 



Of these parts the most important to be attended to are: the median 

 lobe, formed, as we see in Porcellio, by the superior margin of the third 

 or external antennary ring : and the lateral lobes, formed in Oniscus and 

 Porcellio by the superior margin of the same ring, and in ArmadUlium 

 by the inferior margin ; for while undoubtedly generic in their charac- 

 ters, they also assist us materially, in conjunction with other characters, 

 in the formation of families. 



On analysis, then, we get the following types of cephalic characters 

 in the groups : — 



1. Head furnished with lateral lobes arising from inferior margin of 

 third ring ; median lobe arched, prominent, forming a triangular plate 

 vertical to frontal line. Genera — Armadillium, Armadillo, Spherillo (?), 

 Cubaris, Scyphax (?). 



2. (a) Head furnished with lateral lobes arising from superior mar- 

 gin of third ring; median lobe prominent, in the same plane as the 

 frontal line — Porcellio. 



(b) Head furnished with lateral lobes, arising from the superior 

 margin of the third ring, which is emarginate(?) in the centre — Oniscus. 



3. The superior margin of third ring nearly straight, neither lateral 

 nor median lobes, terminating externally at the external angle of orbits 

 — Philoscia, Philougria, Itca(?). 



Itea is described as having small lateral lobes. 



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 antennae ; 

 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 Antenna. 



First, of the Internal antenna, — 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 



