ONISCUS. 467 
inferior border of the cephalic segment which completes 
the orbits.” (Kinahan.) 
The structure of the mouth-organs is described under 
the typical species O. asellus. The first and second seg- 
ments of the tail are visible only in the middle of the 
dorsal surface, the lateral margins of the third segment 
(of which the posterior angles are produced backwards, 
and acute) forms a continuous line with .the lateral 
margins of the last segment of the body. The terminal 
segment is also narrowed at its base; and if we draw a 
line from its outer basal angles to the lateral angles of 
the two basal segments, we shall perceive that the lateral 
margins of the third, fourth, and fifth segments are pro- 
duced outside of this line, and are strictly supplemental 
appendages or lateral lobes. 
The extremity of the terminal segment is produced 
into a narrow and elongated point, its upper surface 
being convex, the basal portion of the terminal appen- 
dages extending to about half the length of this pro- 
duced joint, of which the apex reaches the middle of 
the outer division of the appendage; the inner lobe of 
the basal portion is narrow and elongated, extending a 
short distance beyond the extremity of the tail. 
The species frequent damp situations, and have not 
the power of rolling themselves into a perfect ball, but 
attempt to do this in an incomplete manner, feigning 
death when alarmed. 
HA 2 
