ONYCJIOPHOIIA OF WEST AUSTRALIA. 



373 



The Mandibles, 



The cliaractei' of these striictures has been used very con- 

 siderably in systematic works, and consequently they have more 

 than a little interest for iis liere. 



Each mandible consists as usual of two blades. The outer 

 blade presents a single large projection, but no small teeth. 

 The inner l)lade is provided witli a large principal tooth and a 

 number of smaller accessory teeth. According to Spencer (12) 

 there are four clearly marked and one minute accessory tooth, 

 whilst Bouvier remarks that, as in P. suteri^ P. novce zealanduv, 

 and P. occidentalism there are hve accessory teeth. In the coui'se 

 of this present research the mandibles have l)een removed from a 

 large number of specimens, and examined, with the result that 

 whilst one can say that five accessoiy teeth are most common 

 upon the inner blade, there may be six or even seven. In the 

 latter case the extra teeth are very small. There is again no 

 difference to be noted between the northern variety and the 

 southern form previously known as P. occidentalis. There is never 

 an accessory denticle at the base of the large tooth on the outer 

 jaw blade. 



External Sexual Differences and Crural Papilla. 



There is no difference in the number of legs borne by the two 

 sexes as in Perijmtns novce-hritannice, although the two sexes are 

 to be distinguished hy other characters associated with these 

 appendages, i. e,, the crural papilhe. The female aperture is 

 larger than the male aperture, as noted by Houvier, and both 

 apertures are found between the })a,ses of the legs of the last pair. 

 Behind the aperture of the reprod'ictive organ in the male, and 

 consequently just posterior to the last pair of appendages, are 

 two small openings which can be recognised by their sliglitly 

 tumid, pigmentless lips. These are the apertures of the anal 

 glands. 



The Crural Papilhv are the most distinctive features of the 

 male. Unfortunately there has been some confusion as to tlie 

 number present, and these structures have been taken as of 

 considerable systematic importance. Bouvier (3) gives the 

 following table for three males in his collection (the species 

 formerly known as P. ivoodmardi or P. gilesii) : — 



Legs 1. 2. 3. 4 5. 6. 7. 8. 9. 10.11.12.13.14.15.16. 



Rt. r 1 1 1 1 0 1 1 1 1 1 1 1 1 1 0 0 



Lft. (.1101111111111100 



Rt. riooooooooooiiooo 



Sp. d.] 



Lft. (. 11101111111101 0 0 



Rt. C 1 1 1 0 0 1 1 1 1 1 0 0 0 0 0 0 



Sp.tJ 



Lft. ( 0 I 1 0 0 1 1 1 1 1 1 0 0 0 0 0 



25* 



