687 



CONTRIBUTIONS TO A KNOWLEDGE OF THE AUS- 

 TRALIAN CRUSTACEAN FAUNA. 



No. ii.— On Sacculina, parasitic upon IHhmnopevs serraiifrons. 



By David G. Stead. 



The species treated of in this note — PUiminojiCMS serratifrons, 

 Kinahan — is very abundant in Port Jackson. It is purely a 

 littoral form, and is common on rocky shores, between high- and 

 low-tide marks, wherever there are boulders, under which it 

 seeks concealment. When disturbed, it has the habit of drawing 

 up its legs close to the body and remaining quite still. This 

 enables it often to escape observation entirely, as its dull-coloured 

 body readily assimilates with the surrounding pebbles and debris. 



In colour, it is subject to a good deal of variation. Though 

 usually of a uniform dark brown (with the exception of the 

 external portion of the propodos of each cheliped, which is of a 

 lighter hue), specimens are occasionally met with of a dirty-white 

 colour, this latter variety being connected with the former by a 

 series of intermediate mottled forms. The colour seems to depend 

 in some measure upon the animal's surroundings.* 



The females arrive at maturity at a comparative!}' early age, 

 specimens of very small proportions being found carrying ova. 



Upon an observers examining a good number of these crabs, 

 he will most likely come across one or tAvo which will at once 



* This modification of colour to suit suiroundings is especially conspicuous 

 in another Port Jackson species — Le2)tO(Uux e.raratus — of which there are four 

 varieties, viz., white, red-and-white, black-and-white, and black. 



