MYSIDJ;. 



pointed scale arises from the first joint of the pecluiicle, 

 above the setaceous portion ; this is twice as long as the 

 peduncle, and is thickly fringed with long hairs, which are 

 directed inwardly so as to meet those of the opposite side. 

 The carapace is not very large, curved at its posterior 

 edge, and produced at its posterior and inferior angle. 



" Abdomen slender, the inferior edge of each segment 

 considerably produced, and all of them but the last bear- 

 ing a fin composed of two joints ; the first joint is scale- 

 like clavate ; the second is multiarticulate and plumose ; 

 all of them but the first pair double. The bifurcate con- 

 volute organ, between the double plumes, is very minute. 

 Middle plate of the tail edged with spines on its sides, and 

 entire at the extremity. External caudal fins twice as long 

 as the middle plate, and pointed. 



" The bifurcate and convolute organ between the double 

 plumes of the four last subabdominal fins, together with 

 the number of joints in these fins, seem to be the most 

 striking characters of this genus. Mr. Thompson, in the 

 third memoir of his ' Zoological Researches,' says, ' It is 

 not in the number of joints alone, however, that they 

 (subabdominal fins) differ, their form and structure is also 

 essentially different. In Cynthia the four last of these 

 members are each composed of a very large bilobate scale, 

 supporting at its apex two taper articulate fins, strongly 

 ciliated with plumose setae ; from between these originates 

 an opake organ which bifurcates, its two extremes of 

 unequal length being rolled inwards, the one over the 

 other. 1 



" Mr. Edwards considers that these last are the branchial 

 apparatus. 



