104 A HISTOKY OF RECENT CRUSTACEA 



CHAPTER VIII 



TRIBE III. — OXYRRHYNCHA 



The carapace is more or less narrowed anteriorly and 

 usually rostrate, with the hepatic regions small, the bran- 

 chial large. The epistome is generally large. The buccal 

 frame is quadrate, with the anterior margin straight. 

 There are nine pairs of branchige, with the efferent chan- 

 nels opening at the sides of the endostome. In this, 

 as in the two preceding tribes, the afferent channels 

 open behind the pterygostomian regions, in front of the 

 base of the chelipeds. The first antennge are longitu- 

 dinally folded. The third maxillipeds have the fifth joint 

 articulated at the apex or at the front inner angle of the 

 fourth. The verges of the male are exserted through 

 the bases of the last pair of walking legs. 



This tribe of the ' sharp-snouted ' crabs is divided 

 into two legions, the Maiinea and Parthenopinea. It has 

 been observed in many cases that the two halves of the 

 large liver are not separate, but united by a median lobe. 

 The nervous system is said to attain a higher degree of cen- 

 tralisation in this group of Crustacea than in any other, the 

 ganglia of the trunk forming a single solid disk-like mass. 



Leg ion 1 . — Maiinea. 



The basal joint of the second antennae is well de- 

 veloped, inserted beneath the eyes, and usually occupies a 

 great part of the infra-ocular space. 



This legion contains three families, the Inachidae, 

 Maiidge, and Periceridge. 



Family 1. — Inachidce. 



The eyes are non-retractile, or retractile against the 

 sides of the carapace. In general the orbits are not de- 



