SPHHROMA RUGICAUDA. 409 
having the eyes on each side, which do not touch the 
external margins, and are not quite round in their out- 
line ; the superior antenne are about half the length of 
the inferior; the flat basal joints are punctate; the 
segments of the body are nearly equal, short, and con- 
vex ; the terminal segment of the tail is rounded behind 
and obliquely truncate at the sides; the two plates of 
its lateral appendages are equal, of a linear-oval shape, 
neither ciliated nor serrated on the outer edge. 
When alive, it is of an ashy colour, with dots and 
streaks of black, and is often marked with a light 
coloured stripe down the back; it is much more active 
than the preceding species, swimming with considerable 
velocity and often on its back, and contracting itself into 
a ball when alarmed; it can live a long time out of 
water. 
It occurs on the coasts of France and Great Britain. 
Dr. Leach took it very abundantly on the island of Ulva, 
near Mull (one of the Hebrides), and also at the mouth 
of the River Tamar, in Devonshire. Dr. Johnston also 
sent it to us from Berwick-upon-Tweed, and Dr. Kina- 
han dredged it at Blockhead, in Belfast Bay. 
