446 Dr. H. Woodward—Synopsis of the Species of 
or furrow; the border is sometimes prolonged into a spine at the 
angle of the frée-cheeks. The posterior margin of the head is formed 
by the grooved and furrowed border of the free-cheeks on each side 
and by the two basal lobes, and the neck-lobe, which are separated 
from the glabella by a very distinct and deep furrow; the neck-lobe 
is broader than the free thoracic somites which follow it; the 
glabella is usually rounded and gibbous in front, but does not over- 
hang its anterior border. (Barrande states that there are three pairs 
of short lateral grooves on its surface, although not always to be 
distinguished.) The axal furrows which surround the glabella are 
very distinct; the facial suture (which divides the fixed-cheeks from 
the free-cheeks) crosses the frontal border just in a line with the 
compound eye, above which it expands, forming a rounded palpebral 
lobe, then passing down close to the line of the axal furrow, it 
diverges outwards and crosses the posterior border obliquely behind 
the line of the orbit. The free-cheek is triangular, its surface is 
convex, and upon the highest point is placed the large compound 
reniform eye, which sometimes exhibits a faceted surface or is quite 
smooth according to the state of its conservation. 
Free thoracic segments varying from 8 to 10 (Proetus Barrandii, 
Roemer, Devonian, Harz, has 8 somites; 9 and 10 is the common 
number for the Silurian species). The axis is always strongly 
arched, and does not exceed the pleuree in breadth; the breadth of 
the axis diminishes very gradually to the posterior extremity ; the 
pleurze are more or less bent at the fulcral point, and have their 
extremities either pointed or rounded and their anterior margin 
faceted for rolling up. 
The pygidium varies in its elevation, but the axis is always raised 
above the margin and diminishes to a blunt extremity, leaving a 
smooth border beyond; the number of coalesced segments in the 
tail-shield varies (Barrande says from 4 to 15 in species found in 
Bohemia) ; the pleuree do not extend to the margin of the pygidium, 
which is often smooth. 
The surface of the test is most frequently smooth or finely granu- 
lated; in a few species it is striated, and rarely it presents a com- 
bination of both kinds of ornamentation. 
Prortus? Levis, H. Woodw. sp. nov. 
p 
Phillipsia Brongniarti?, Baily, 1875. Mem. Geol. Surv. Ireland, Expl. Mem. 
Sheets 102 and 112, 2nd ed., p. 19. 
Pygidium of Proetus ? levis, H. Woodw. 
Carboniferous Limestone, Moneenalion, Co, Dublin, Enlarged nearly twice natural size. 
