!^68 



THE INTER-COXAL LOBE OF CERTAIN CRAYFISHES, 



the^birt!! "^ T\ '^^"•^"^' '^'' " ^''' ^^P^«^^ - removing 

 the base of the podobranchia is somewhat of an oblong in shape 



lolTf 'f , " '""^^"^^''' ^°"^"^' ''^''' - -1-r, and free 



colou. and covered wxth set. which project prominently from 



:: Ih!::!'"' ''- ''''-' -' '-- ^-^^- ^^ ^^^^ '-^-^ 



The anterior face mentioned above as being applied to the base 

 of he coxopodi e, xs triangular in outline, concave, dark in colour 

 and covered wxth set.. The lower portion of this face is chitinous ' 

 the uppex- mexnbranous, being in fact a continuation of the 

 artni'oaxal membrane. 



The posterior face of the body is concave, lower portion 

 chxtxnous and covered with set. ; the upper free from set. and 

 menxbranous. Thus from the concave shape of the anterior fa ^ 

 he by ,3 able to fit well on the convex base of the coxopodite 

 vhx e xts posterxor concave surface likewise fits the convex anterio^ 

 border of the coxopodite of the followixxg thoracic limb when this 

 iimb xs in a forward position. 



The inter-coxal lobe would thus appear to act as a valve between 

 the thoracxc Ixmbs and the branchiostegite, preventing the too 

 ready entrance of foreign bodies. 



Many forms were examined to ascertain if this inter-coxal 

 lobe was present. In Asiacus JluviatiUs it is entirely absent 

 as such the only representative beixxg a small hard ridge on 

 the arthrodxal membrane of the fourth pair of le^s In 



tf Tr.-.r^''"" "'' '"^'^ "'^"^ ^^ *h^ *^«racic limbs of 



bth-1.3th XX clusxve. lu Ibacus and Arctus they become calcified 

 an^d^ quite immovable, being attached to the arthrophragm of t"e 



No representative of this structure was found in axiy of the 

 Anomura or Brachyura examined. 



The absence of axxy exopodite in the thoracic appendages of 



* The Crayfish, page 219. 



