THE BRACHYURA. 297 



it out into certain definite regions of considerable systematic 

 importance. An irregular transverse depression, crossing the 

 carapace near the anterior margin, bounds an anterior or fa- 

 cial region, divided into a middle J'ro?ital lobe (/), and lateral 

 orbital lobes (o), from a posterior, much larger, gastro-hepatio 

 area, divided into small lateral he2Xitic lobes (A), and a large 

 complex gastric lobe (^\ ^^, etc.). Tlie latter is again sub- 

 divided into two ejngastric lobes (^'), two protogastric lobes 

 (^'^), a median onesogastric lobe (^^), two metagastrlc lobes 

 ((/*), and two iirogastric lobes (^^), making altogether nine 

 subordinate divisions. The gastric lobes correspond in a gen- 

 eral way to the stomach ; the hepatic lobes, to a portion of 

 the liver. The region behind the cervical suture consists of 

 the connate terga of the eight thoracic somites ; it is divided 

 by two strong longitudinal grooves, the hranchio-cardiac 

 grooves, into a middle region, corresponding with the heart, 

 and two lateral regions, forming the roof of the branchial 

 chamber. A transverse depression divides the middle region 

 into an anterior and a posterior cardiac lobe, while the bran- 

 chial region is subdivided into epibranchial (b^)^ mesobran- 

 chial (6^), and nietabranchial (b^) lobes. 



On turning to the inflected inferior portion of the cara- 

 pace, a sutural line or groove is seen running from the epi- 

 stoma, outward and backward, very nearly reaching the outer 

 edge of the carapace, opposite its external angle, and then 

 sweeping backward parallel with, and but little distant from, 

 its postero-lateral boundary, until it cuts its posterior edge. 

 The portion of the carapace internal to this sutural line is 

 called by Milne-Edwards the inferior branddostegite^ and is 

 considered by him to be composed of an anterior {ep) and 

 posterior epimeral piece, corresponding with the subhepatic 

 (sh) and subbranchial regions of the surface of the carapace 

 between the suture and the line of inflection. I cannot 

 regard these parts, however, as having any relation with the 

 true epimera. The suture, or rather groove, seems rather to 

 correspond with that which marks off the pleuron from the 

 rest of the somite in Astacus. 



The anterior cephalic somites in Carcinus have under- 

 gone some singular modifications, whereby their true relations 

 are greatly obscured. The broad trilobed plate (Fig. 76,/) 

 corresponds with the elongated rostrum oi Astacus ; inferiorly 

 it is produced in the median line into a strong ridge or sep- 

 tum, the lower and posterior edge of which is convex, and 

 fits closely into the concavity formed by the antennulary and 



