296 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



stoma ; and the plate which stretches backward and supports 

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

 do stoma. 



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. ?6, cs). Further than this I 

 cannot trace this homologue of the cervical groove of Astacus. 



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

 pace of Carcinus mcenas : f, rostrum; o, orbit; cs. cervical groove; g 1 , epigastric 

 lobe; gr 2 , protogaetric ; <7 3 , nasogastric ; g*, hypogastric: g 5 , urogastric; c, e 1 , an- 

 terior and posterior cardiac; h, hepatic; b 1 , ft 3 , b 3 . epibranchial, mesobranchial 

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

 terior half of the same carapace: a, rostral septum; b. autennary sternum ; c, 

 suture between these; d, supraciliary lobe; e. internal suborbital 1 lobe ; /, anten- 

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

 nule; o, orbit ; eh, subhepatic region; ep, anterior pleural region. The riglit- 

 hand upper figure gives a side-view of the carapace of Stenorhyhchiis phalangiiim, 

 the common "spider-crab:" o. orbit ; /',/ 2 , rostrum ; al, autennule ; at, antenna ; 

 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 



