4,94, SPHHROMIDA. 
~~ 
into a flattened triangular lobe, the centre of which is 
longitudinally impressed. The hind margin is also fur- 
nished on each side (about half way between the middle 
and lateral angles) with a minute but prominent tubercle. 
The terminal segment of the tail is very convex, with a 
transverse bipartite tubercle in the middle; the terminal 
margin is incised in the centre with a small longitudinal 
slit. The outer plate of the lateral appendages of the 
tail is narrowly ovate, and pointed at the tip; it is 
somewhat longer than the inner lobe, which is slightly 
obliquely truncated. 
This species was taken by Dr. Leach on the western 
shores of Devonshire, and named in honour of Colonel 
Montagu, whose researches on marine zoology added so 
greatly to our knowledge of the native fauna. We 
have taken it among Fuci, between tide marks on the 
coast of South Wales, South Devon, and Cornwall. 
It is probably tolerably common on rocky beaches all 
round our coast. It is generally found associated with 
Dynamene rubra and Nesa bidentata. 
