35 
corresponds one of the ridges or slightly angular annnlations with which the 
outer surface is provided. The surface appears to have been smooth and the 
shell very thin. The siphuncle, its position, as well as the shape of the last 
septum or body chamber, are quite unknown to me. 
Dimensions. — The apical angle being only 4° to 5°, this species must 
have been more than fifteen centimetres long, supposing that the growth was 
regular. In a specimen a centimetre in diameter the height of each chamber 
is about two millimetres. 
Horizon and Localities. — In England this species occurs in the Ejiper 
Silurian of the Ludlow District. In Australia it is associated with the 
preceding species. 
CEUSTACEA. 
Order — OSTRACODA. 
Genus — ENTOMIS, Riipert Jones. 
Entomis pelagica, Barrande. 
Bntomis pelagica, J. Barrande, 1872, Syst. SIl. Boheme, I, Suppl., p. 515, pi. 21, fig. 1-6. 
In form the valves are suhsemicircular ; this is caused by the curve 
that hounds the two ends of the hinge line, which is straight or slightly 
sinuous for the rest of its length. 
Each of the two valves is divided into almost equal parts by a fairly 
deep and slightly sigmoidal furrow, which, springing from the hinge line, 
ends at a little distance from the opposite l)order. Doth these portions are 
arched, hut the convexity of the lower portion is more regular than that of 
the cephalic, which is distinguished by a well-marked tubercle on the margin 
and almost opposite the middle of the transverse furrow. The remain of the 
surface of this portion is faintly undulated. The two valves are quite smooth; 
the test seems to have been very thin. 
Dimensions. — The sole sjoecimen observed is only three millimetres 
long by about two broad. Although these dimensions are a little different 
from tliose given by Barrande (six millimetres by about three), I have not 
thought it advisable to separate the Australian from the Bohemian species, as 
all the other characters agree with great exactitude, particularly the well- 
marked cephalic tubercle, which serves to distinguish it from its congeners. 
G 
