68 ME. F, R. C. REED ON THE GENUS LICHAS. [ Feb. 1902; 
slightly ; in some cases they are small and obviously cut out of the 
neck-ring (as in Lichas verrucosus) ; in others they are comparatively 
large and triangular (as in L. pachyrhina) and have encroached 
upon the glabella. 
It is possible that in some cases in which occipital lobes are now 
absent, they may have disappeared owing to a secondary fusion with 
the fourth lateral lobes. This may have happened in Lichas anglicus, 
L. hirsutus, Acanthopyge Haueri, etc., and may be regarded as 
another mark of the wide departure from the ancestral type which 
these and allied species have made. 
Spinose processes, generally paired, may be developed on the 
glabella, as, for example, in Arges armatus. 
There are a few species in which the bi-composite lateral lobes 
appear to extend for practically the whole length of the glabella; 
and the cause appears to be that the fourth lateral lobes have been 
squeezed out and obliterated by a shortening and condensation of 
the head-shield at their expense. Such are the species Oncholichas 
ornatus and Lichas gotlandicus, in which the single pair of lateral 
lobes appears not to be due to an incorporation and fusion of the 
fourth lateral lobes with the bi-composite pair, or to a prolongation 
backward of the first lateral furrows te the occipital furrow. The 
traces of the second lateral furrows across these lobes are fairly 
distinct. We shall see that the pygidial characters of these species 
support the conclusion that they belong to this first stage, and not 
to the second one which is now to be described. 
IJ.—The second stage in the evolution of the glabella is marked 
by the first lateral furrows not ending their backward prolongation at 
the third lateral furrows, but continuing to the occipital furrow in 
a regular course which may be almost straight or concave outward. 
A single long median lobe to the glabella is thus formed, extending 
from its anterior end to the neck-ring, and it is bounded on each 
side by a single long lateral lobe composed of the fused second, 
third, and fourth lateral lobes. The presence of this pair of tri- 
composite lobes is the distinguishing feature of this second stage. 
The intermediate or transitional condition between the first and 
second stages is indicated in a few species (such as Hoplolichas tri- 
cuspidatus, Lichas conicotuberculatus), in which there is a slight 
deflexion in the course of the first lateral furrows opposite the third 
lateral furrows, and behind the latter they are less deeply impressed. 
The occasional persistence of the third lateral furrows across the 
single tri-composite lateral lobes indicates also a transitional state, 
but it is doubtful whether we possess any examples on the direct line 
of descent of the second from the first stage, and it is possible that 
the second line of mcdification proceeded parallel to the first from 
a common stock. In the most completely developed members of 
this stage the course of the first lateral furrows is a regular curve 
or continuous straight line of uniform strength, and the third lateral 
furrows have completely disappeared (as in Lichas hibernicus). 
