296 



THE ANATOMY OF IXVERTEBRATED ANIMALS. 



Stoma / and the plate which stretches backward and supports 

 the labrum, within its posterior forked boundary, is the en- 

 dost oma. 



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 jLstacus, 



Fia. 76.— Of the two nppcr fisrnres*, the left represents the dorsal surface of the cara- 

 pace of Carcinus mmnas : f, ros?trum; o, orbit; cs, cervical grouve; gri, epigastric 

 lobe; 9^2 protogaetric ; g»3^ mesogastric ; g^*, hypogastric; g'^ urogastric; c, c\ an- 

 terior and posterior cardiac ; h, hepatic ; 6', ^>^ b^, epibrancbial, mesobranchial 

 and mefabranchial lobes. The lower figure represents a ventral view of the an- 

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

 suture between these ; c?, snpraciliary lobe ; e, internal suborbitar lobe ; /, anten- 

 na ; g, articular cavity for the ophthalmic peduncle ; h, tlie same for the anten- 

 nule; o, orbit ; .s,^, subhepatic region; f/?, anterior pleural region. The riglit- 

 hand upper figure gives a side-view of the carapace of SfeJiorhynchvs pkalanginm, 

 the common " spider-crab : " o, orbit ; f^f"^, rostrum ; al, auteunule ; at, auteuua ; 

 ep, 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 



