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- 

 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. 



o A 



..'* 3 A 



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; <7 2 , protogastric ; g 3 , nasogastric ; g*, hypogastric ; g 5 , urogastric ; c, c 1 , an- 

 terior and posterior cardiac ; h, hepatic; b 1 , b 2 , b s , 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, supraciliary lobe; e, internal suborbitar lobe ; /, anten- 

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

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

 hand upper figure gives a side-view of the carapace of Stenorhynchus phalangium, 

 the common "spider-crab:" o. orbit j/ 1 ,/ 2 , rostrum ; al, antennule ; 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 



