43 
fairly narrow, while they are shown as being deep and as broad as the ribs in 
the first-mentioned species. Pinally, all tlic specimens examined having lost 
their eyes, I have been unable to investigate either the shape or position of 
those organs. 
Horizon and Localities. — According to Barrande, this species is char- 
acteristic of the lower calcareous Etage E. of his sul)division of the Upper 
Silurian, and has been found at Tobolka, Wohroda, &c., associated with 
Cromus Beaumonti, Barrande, Cheirurus insignis, Beyrich, and numerous 
other Trilobites. Under analogous conditions the species has been collected 
in a grey argillaceous limestone at Yarralumla. 
2. Cromus Murchisoni, L. G. de Koninck. 
PL I, fig. 9. 
This species, the head of which aj)pears to me to have a sub-semi- 
circular outline, is singular in the shape of the glabella, which is almost the 
only well-preserved part of the specimen submitted to me. The glabella is 
club-shaped, the anterior or frontal portion is about twice as wide as the 
posterior ; the anterior portion is depressed while the posterior is sub-semi- 
cylindrical ; this portion has four unbroken furrows forming ridges, each 
with five tubercles. The surface of the anterior portion is also ornamented 
with a large number of similar tubercles. The glabella is clearly separated 
from the fixed cheeks by curved very deep longitudinal furrows. The fixed 
cheek in convex near the glabella, and is of the same width. The eye is pro- 
jecting, and is surrounded on the side of the palpebral lobe by a semicircular 
groove. The free cheek and the genal angle are unknown to me ; the same 
applies to the thorax and pygidium. 
Relations and Differences.— Cromus Murchisoni is distinguished from 
all known congeners by the shape of the glabella and the depth of the furrows 
which separate it from the fixed cheeks. 
Horizon and Localities. — A very imperfect specimen, associated with 
the preceding, has been found at Yarralumla, and another which has served as 
the subject of my description has been collected at Quedong in a greyish 
argillaceous limestone. 
H 
