SPHiEROMA. 245 



Sph^eroma serratum, Fabr. sp. Serrated Sea Pill-ball. 

 (Plate XIII. fig. 6.) — Body smooth; tail very smooth, 

 obliquely truncated on each side, the lamellae elliptical, 

 sharp, the outer serrated externally. 



Of an ashy colour, or whitish marbled with red. 



Rocky shores ; very common. 



SphjEROma rugtcauda, Leach. Rough-tailed Sea Pill- 

 ball. — Body smooth ; tail rough, with its lamellae rounded, 

 the outer scarcely toothed externally. Body ash-coloured, 

 lineated, and spotted with black. 



Island of Ulva; where it was found by Dr. Leach. Ber- 

 wick-upon-Tweed (Dr. Johnston). 



SpHiEROMA Hookeri, Leach. — Body smooth ; the last 

 joint of the tail furnished with two oblong tubercles. Ash- 

 coloured or reddish, with minute black punctures. 



Coast of Suffolk, whence it was sent by Sir Wm. Jackson 

 Hooker to Dr. Leach. The Rev. Alfred Norman finds it 

 at Clevedon and in Guernsey. 



There are other recorded British species, but they are 

 but imperfectly characterized. 



