Vol. 58.] MR. F, R. C, REED ON THE GENUS LICHAS. 71 
species, with its well-developed lobes and furrows, it may easily 
be seen how the other species above-mentioned are derived by the 
suppression of certain furrows and the fusion of certain lobes. 
Modifications in the pygidium may also set in, such as the loss 
of the lateral spines ; but the important features of (1) the possession 
of two complete pleura, each well marked out and with pleural 
furrow ; (2) the non-furrowed surface of the posterior portion of the 
lateral lobes; and (3) a definitely circumscribed axis and no broad 
post-axial piece, are retained. 
Fig. 1.—Lichas palmatus, Barr. (After Burrande.) 
ee 
b 
fa from ‘Syst. Silur. Boh,’ pl. xxviii, fig. 7; 6 from pl. xxviii, fig. 9.] 
a 
A large number of species fall into this Section A of Group I, 
nearly all of which seem to be of Silurian age. The type-species 
of Acanthopyge | = Euarges, Giirich], Corydocephalus | = Plusiarges, 
Girich], Dicranogmus [ =Liparges, Giirich], and Hemiarges belong 
here, as well as many others which have been wrongly ascribed 
to Arges.’ 
Section A. 
LI. (Corydocephalus) palnatus, Barr. | L. scutalis, Salt. 
L. (Acanthopyge) Haueri, Barr. | L. ambiguus, Barr. 
L. (Dicranogmus) simplex, Barr. L, heteroclytus, Barr. 
L. anglicus, Beyr. L. (Hemiarges) wesenbergensis, 
L. hirsutus, Fletch. Schm. 
Lichas palmatus may be regarded as the type of this group, as it 
possesses the most complete development of the head-shield, lobes, 
and furrows, and all the important sectional features of the pygidium. 
(The four above-mentioned subgenera recognized by Dr. Giirich 
(EHuarges, Plusvarges, Liparges, and Hemiarges) which are associated 
together in this section may be regarded as subsections, though hardly 
of subgeneric value. Craspedaryes Wilcannic is closely allied to 
Euarges and Henvarges in its cranidial characters, but on account of 
its peculiar yet imperfectly known pygidium it must for the present 
be put doubtfully in another subsection by itself. ] 
Section B. (Fig. 2, p. 72.) 
Of this next section which may be recognized in Group I, we appear 
to know only one complete example, Dicranopeltis {= Trachylichas, 
Giirich ] scabra, and the characters of its head-shield may be regarded 
as typical of the section. But, from the resemblance of certain other 
1 Only a few examples are given in each section, and no complete list of the 
species is attempted. 
