406 SPH^ROMID.E. 



Oniscus glohator. Pallas, Spic. Zool. ix. t. 4, f . 18. 



Sphceroma cinerea. Bosc, Hist. Crust. 11, p. 186. Latreillb, Hist. n. 

 Crust, et Ins. vii. p. 16. Genera Crust, et Ins. 1, 

 p. 65. Savigny, Exped. Egypt. Crust, t. 12, f. 1. 



This is the largest British species, sometimes attaining 

 the length of half an inch. It is very convex, and has 

 the surface of the body quite smooth. It is broadly 

 ovate, the greatest breadth being in the middle of the 

 animal. The front of the head is nearly straight, and 

 elevated into a thin marginal line, in the middle of which, 

 beneath, is affixed the small triangular piece between the 

 base of the superior antennae, the two dilated basal joints 

 of which do not extend to the inner angle of the eyes, 

 whilst the flagellum extends slightly beyond the base 

 of the flagellum of the lower antennae. The seventh 

 segment of the body (pereion) is very short, and on each 

 side, near the extremity of its posterior margin, is a 

 small, somewhat triangular incision, which is filled up by 

 a minute but distinct rudimental portion of the real first 

 segment of the tail, of which no other portion is visible ; 

 the first apparent segment consisting of three joints, of 

 which incisional traces may be observed in the two lines 

 on either side, which are quite lost in the middle of the 

 disc, which is quite smooth, simple, and entire. The ter- 

 minal segment is very convex ; it is narrowed on each 

 side for the recejDtion of the flat curved inner lobe of the 

 lateral appendages (uropoda), beneath which the outer 

 lobe is generally concealed ; thus forming, with the ter- 

 minal segment of the tail, nearly a semicircle, of which 

 the posterior extremity is slightly truncate. The outer 

 margin of the lateral appendages is furnished with five or 

 six serrations. Sometimes the posterior extremity of the 

 tail is somewhat elongated into a flattened and more 

 truncated plate, in which state it appears to have been 



