70 MR. F, R. C. REED ON THE GENUS LICHAS. [Feb. 1902, 
V. CLASSIFICATION OF THE LICHADID. 
From the foregoing considerations we see that, on the evidence of 
the head-shield and lobation of the glabella, the members of the 
Lichadidee fall into two great groups corresponding to the two stages 
above described. There is (1) the group with a pair of bi-composite 
lateral lobes to the glabella, and a more or less definite fourth pair 
of lateral lobes; and (2) a group with a pair of tri-composite 
lateral lobes, originating by the fusion of the fourth pair with the 
bi-composite pair of the preceding group. 
The types of the subgenera or genera previously given are 
distributed as follows between these two groups, in so far as their 
crapidial characters are concerned :— 
Group I. 
Acanthopyge Haueri. Hemiarges wesenbergensis. 
Arctinurus Boltoni. Lichas laciniatus. 
Arges armatus. | Metopias Hitbneri. 
Corydocephalus palmatus. | Oncholichas ornatus. 
Craspedarges Wilcannie. Platopolichas avus. 
Dicranogmus simplex. Platylichas margaritifer. 
Dicranopeltis scabra. Uralichas Ribetrot. 
Grovr II. 
Ceratolichas gryps. Hoplolichas tricuspidatus. 
Conolichas equiloba. Leiolichas illenvides, 
Echinolichas Eriopis. Platymetopus lineatus. 
Homolichas depressus. Terataspis grandis, 
These two groups, in which the original and usual subgeneric 
names applied to different species have been used in order to show 
their proper place in this scheme, can be further subdivided. 
Group I. 
Section A. (Fic. 1, p. 71.) 
It has been pointed out that closely allied forms can have the 
furrows and lobes of the glabella in either of these groups modified 
to a considerable extent within the limits of the group-characters ; 
and the pygidia may retain certain common features in spite of all. 
Thus Acanthopyge Haueri and Dicranogmus simplex have closely 
similar head-shields, though in the latter the anterior portion of the 
first lateral furrows is wanting, a condition which we see com- 
mencing to develop in Lichas anglicus, where these furrows are weak 
anteriorly. In dA. Hauwert and L. anglicus and in the American 
species of Dicranogmus we find a precisely similar type of pygidium, 
consisting of two complete pleurz on the lateral lobes, two distinct 
rings on the axis followed by several indistinct annulations, and a 
narrow post-axial ridge. The rest of the lateral lobes behind the 
second pair of pleure is not traversed by any furrow. Three principal 
pairs of spines represent the free ends of the pleuree. Corydocephalus 
palmatus has a similar pygidium, and from the head-shield of this 
