110 MR. R. GURNEY ON LEANDER LONGIROSTRIS 



entirely obscure the red. In such cases, which are rare, the 

 animal appears of a very dark purple-black colour. Occasionally 

 the red pigment alone is present, the blue being suppressed, such 

 specimens appearing of a beautiful rosy colour, the margins of 

 the abdominal segments being more deeply coloured. An 

 unusually large female (75 mm.) of this type was taken in the 

 River Bure in Jvily 1922, and has lived in a fresh-water 

 aquarium for over three months without losing its red colouring. 

 There is a tendency for the chromatophores to become arranged in 

 more or less conspicuous lines and patches (text-fig. 3), but these 

 do not give the appearance of distinct bands as in L. squilla and 

 L. serratus. The limbs are usually colourless, except for a few 

 scattered red chromatophores, but there is sometimes a faint blue 

 colour on the chelae. 



Length. — Female (bearing eggs) 50 to 77 mm. Male 35 to 

 77 mm. Usually much smaller than the female. 



Rostrimi. — The rostrum projects considerably beyond the 

 antennal scales, and is deep and nearly straight, but commonly 

 slightly upcurved. It is usually armed with 8 dorsal and 4 

 ventral teeth, the dorsal teeth being rather prominent, as in 

 L. squilla. The first two teeth are situated behind the eye, the 

 third just in front of the orbital notch. As has been pointed 

 out by De Man, it is particularly characteristic of this species 

 that the space between the first two teeth is one-and-a-half times 

 as great as that between the second and third. The following 

 figures show the variation in the number of rostral teeth in 191 

 females from Norfolk : — 



8-f-l 



In Norfolk, therefore, the usual formula is -^, but De Man 



7+1 

 foundHhe usual formula for Dutch specimens to be —^ and 



that the dorsal teeth varied from 12 to 6. I have excluded 

 males fi'om my table, but have no reason to believe that they 

 difi"er in this respect from females. The number of teeth does 

 not increase with age or size, and the smaller size of the male is 

 not of itself likely to reduce the average number of rostral teeth. 

 I have not in all cases noted the number of small apical teeth, 

 but in 46 specimens only 3 had two of these teeth, whereas 

 De Man found this number in 42 per cent. The difierence may 

 perhaps be explained on the assumption that the proximal 

 apical tooth, when present in Norfolk specimens, is larger and 

 less separated from the others, and has therefore been counted in 



