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 r 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. 



H H 2 



