296 



THE ANATOMY OF IXVERTEBRATED ANIMALS. 



stoma ; and the plate which stretches backward and supports 

 the iabrum, w^ithin its posterior forked boundary, is the e/i- 

 dostoraa. 



The middle of the dorsal surface of the carapace is marked 

 somewhat nearer its posterior than its anterior boundary by 

 a short transverse depression, which is continued on each side 

 forward and outward, and then curves directly outward to the 

 edge of the carapace (Fig. 76, cs). Further than this I 

 cannot trace this homologue of the cervical groove of Astacus. 



Fig. 76.— Of the two upper fi^iiref, the left represents the dorsal surface of the cara- 

 pace of CarcinuH mmnaft : f, roctrum; o, orbit; C8. cervical f^roove; g^, epit-aetric 

 lobe; fj"^, proto<4af-tnc ; gr^, me«oj?a8tric ; g'^, hypogastric: g^, uro^aetric; c, c', an- 

 terior and posterior cardiac; h, hepatic; i', i»*, 6^, epibrancliial, mebobranchial 

 and metabrancliial lobes. The lower fit^nare represents a ventral view of the an- 

 terior half of the same carapace: a, rostral septum: 6, antennary sternum ; c, 

 suture between these ; ri, supraciliary lobe ; <?, internal suborbitar lr)be : ./; anten- 

 na ; 7, articular cavity for the ojjhthalmic peduncle ; h^ the same for the anten- 

 nule; 0, orbit ; /?A, subhepatic retrion; z^;?, antcri<*r pleural rej^ion. The ri<rht- 

 hand upper fii^ure t,dves a side-view of the carapace of Stf-nf/rhynchufi phalamfiiim, 

 the common ■■' spider-crab : " o. orbit ; f\f^, rostrum ; al, anteunule ; at, antenna ; 

 cp, epistoma. 



Elevations and depressions upon the surface of the carapace 

 in front of the cervical groove, which, as in Astacus^ is com- 

 posed of the connate terga of the six cephalic somites, mark 



