INTRODUCTION. Xlll 



pairs are represented by appendages which serve for the attach- 

 ment of the eggs, and in the male two pairs of styliform appen- 

 dages having the function of external reproductive organs are 

 connected with the first and second segments. 



Fig. II. Diagramic view of the upper surface of carapace of a Crab, shewing 



the position of the regions. 



fr, Front ; o, eye ; g, epigastric region ; g', protogastric ; g", nasogastric ; 

 g" : , metagastric; g 1 " 1 , urogastric; h, hepatic region; cs, portion of cervical 

 groove ; iri, epibranchial region ; br *, mesobranchial ; br*, metabranchial. 



The carapace is flatfish, or gently convex above, and turns 

 down suddenly at the sides so as to form a well-marked border. 

 Below it fits down closely over the bases of the thoracic limbs, 

 leaving only a small space in front of the great chelipedes or 

 pincer-claws for the ingress of the water to the gills. The 

 surface of the carapace of the Crab is generally marked out by 

 grooves into certain regions. The space between the eyes is 

 termed the front (Fig. \\.,fr.) ; in some Crabs, as in the Prawn, it 

 is drawn out anteriorly in the form of a beak or rostrum. Behind 

 the front is the gastric region (g), so called from its corresponding 

 in a general way with the situation of the stomach within the 

 carapace ; the gastric region is sub-divided frequently into 

 certain subregions ; these are usually a small anterior epigastric 

 region (a), followed by two larger protogastric regions (g 1 ), 

 behind and between which is a single mesogastric region (g") ; 

 external to the mesogastric region on each side is a hypogastric 

 sub-division (g'") ; and behind these a mesial urogastric (g""). 

 Behind the gastric region is the cardiac (c). Between the gastric 

 region and the anterior portion of the antero-latcral borders of 

 the carapace is the hepatic region (h) . Behind the hepatic region 



