266 PROCEEDINGS OP SOCIETIES. 



The superior margin of the third ring commences beneath the lateral 

 lobes of the cephalic segment, a suture marking its origin, and the margin 

 of cephalic border concealing it, thence it gradually emerges, passing in- 

 wards, and rises above the frontal border as a prominent arched plate, 

 which projects over the frontal line, and is visible from behind. 



Its surface presents the following markings, beginning below : — In 

 the* centre, arising from the transversal suture which divides the second 

 and third segments, two divergent ridges passing out on each side, termi- 

 nate at the extremities of the arched superior margin ; external to each 

 of these is a deep sulcus ; bounding the outer edge of this sulcus a curved 

 raised ridge surrounds the insertion of each external antennae, and termi- 

 nates as a large lobe on the outer side of the head ; these are the lobes 

 which are described by authors as the lateral lobes in the Armadillinae, 

 and which differ from the lateral lobes of the Oniscinae in the place of 

 their origin being from the inferior, not superior, margin of third ring. 



The second ring is well marked, transversal, and prolonged on each 

 side into a trigonal point beneath the external antennae, the lobes bear- 

 ing the internal antennae on their summits. "When at rest the external 

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

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

 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 Armadillium 

 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, Itea(?). 



Itea is described as having small lateral lobes. 



