102 MB. R. GURNEY ON LEANDER LONGIROSTRIS 



2. Leander squilla (Linn.). 



Colour. — Both thorax and abdominal "segments bear dark 

 yellow-brown bands, which are usually very conspicuous, and are 

 retained for a long time even in specimens preserved in formol, 

 though rapidl}' disappearing in spirit. The rostrum is sometimes 

 quite colourless, bud generally small red chromatophores are 

 scattered over it or arranged in a median row. Kemp states 

 that the rostrum is witliout chromatophores, but this is excep- 

 tional in my experience of Norfolk specimens. The eye-stalks 

 and peduncles of the antennules are deeply pigmented with 

 purple-brown, and the same is the case with the basipodite and 

 ischium of the third, and sometimes of other, legs. The joints 

 of the legs are marked by bands of yellow pigment, and the palm 

 of the chela of the second legs is bright blue. The intensity of 

 the colour seems to vary to some extent with locality and season. 

 In the summer of 1921 all the prawns, of all ages, taken in 

 Wells Harbour, were brilliantly coloured as described above, the 

 blue of the chelae being particularly conspicuous. But others 

 taken from rock-pools at Whitsand Bay in the spring of 1922, 

 though showing the same distribution of colour, were by no 

 means conspicuously banded. They could, however, be im- 

 mediately distinguished from L. sert-atus of the same size by 

 their darker colour. Again, the colouring of the prawns in 

 Wells Harbour during the summer of 1922 was far from being 

 so pronounced as in the previous year, and many, particularly the 

 males, were found to be almost colourless. The bhie colour which 

 was so striking a feature of the chelse in 1921 was seldom 

 brilliant, and often absent, in 1922. 



Length. Male 28-50 mm. Female 30-63 mm. 



The great range in size is due to the fact that maturity is 

 reached in the first year at an average size of about 40 mm. for 

 females and 30 mm. for males. Females over 50 mm. may be 

 assumed to be two years old, and it is probable that those of 

 60 mm. and more are in their third year. 



Rostrum broad, very slightly upcurved, armed dorsally with 

 7-9 teeth, two of which are placed behind the eye, and the third 

 above or slightly behind it. A minute apical tooth is almost 

 invariably present in addition. Ventral teeth usually three. 

 The number of these teeth varies within very narrow limits. 

 For 114 females from Wells, in Norfolk, the number of teeth 

 was as follows : — 



Dorsal teeth : 9 8 7 6 



No. of individuals : 12 65 36 1 



10-5 o/o 570/0 31-50/0 -86 0/0 



Yentral teeth : 4 3 2 



No. of individuals : 1 112 1 



•86 0/0 98-2 0/0 -86% 



