424 SPH^ROMID.E. 



into a flattened triangular lobe, the centre of which is 

 longitudinally impressed. The hind margin is also fur- 

 nished on each side (abov;t 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 

 Df/namene rubra and Nasa bidentata. 



