406 SPH EROMID. 
Oniscus globator. Pauwas, Spic. Zool. ix. t. 4, f. 18. 
Spheroma cinerea. Bosco, Hist. Crust. 11, p. 186. Larreruuy, Hist. n. 
Crust. et Ins. vii. p. 16. Genera Crust. et Ins. 1, 
p. 65. Savieny, Exped. Egypt. Crust. t. 12, f. 1. 
Turs 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 antenne, 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 antenne. 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 reception 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 
