296 THE ANATOMY OF INVERTEBRATED ANIMALS. 



stoma ; and the plate which stretches backward and supports 

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

 dostoma. 



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 figures, the left represents the dorsal surface of the cara- 

 pace of Carcinus mc&nas : /, rostrum; 0, orbit; cs, cervical groove; fir 1 , epigastric 

 lobe; g-, protogastric ; ^ 3 , mesogastric ; g*, hypogastric ; 6 , urogastric; c, c 1 , an- 

 terior and posterior cardiac ; A, hepatic ; 6 1 , 5 2 , 6 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. antennary sternum ; c, 

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

 na ; <7, articular cavity for the ophthalmic peduncle ; A, tlie same for the anten- 

 nnle; o, orbit ;_A, subhepatic region; ep, anterior plenral region. The riglit- 



~ ' enorhynchus phalangium, 

 . antennule ; at, antenna ; 



hand'upper figifre gives a side-view of the carapace of Stenorhynchus phalanglum, 

 the common spider-crab : " o. orbit ; .X" 1 ,/ 2 , rostrum ; a/, ; 



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 



