330 A HISTORY OF RECENT CRUSTACEA 



CHAPTER XXII 



TRIBE II. FLABELLIFERA 



THE name refers to the circumstance that in all the 

 members of this tribe the terminal segment in conjunction 

 with the uropods forms a caudal fan as in the Macrura, 

 although here the telson is often not articulated, but fused 

 with the preceding segment. The heart is situated chiefly 

 in the pleon, only penetrating one or two of the terminal 

 segments of the perseon. Respiration is effected by the 

 help of pleopods acting as branchiae. 



The families included are the Anthuridas, Gnathiida3, 

 Cymothoidas, Serolidas, Sphasromida?, and Limnoriidas. 

 The term Cymothoidaa is used comprehensively for a 

 closely connected group of families, as will be explained 

 hereafter. 



Family I. Anthuridce. 



The body is long and narrow, subcylindrical or 

 depressed. The head is usually shorter than the following 

 segment. The perason has its seven segments distinct. 

 The first five segments of the pleon may be all distinct or 

 completely or partially coalesced ; the sixth is sometimes 

 fused with the linguiform telson. The mouth-organs are 

 suctorial. The first gnathopods are usually the larger, 

 subchelate ; the second gnathopods and first perasopods re- 

 sembling them in general form. The other pera3Opods are 

 ambulatory. There appear to be no separate marsupial 

 plates. The first pleopods are large, commonly expanded 

 to cover the rest. The uropods have a two-jointed inner 

 branch, and the one-jointed outer branch usually so arti- 

 culated as to arch more or less over the back of the telson. 



