THE ISOPODA 



199 



operculum to cover the lateral parts of the other oral appendages. 

 The basipodite is produced distally into a large endite (I 2 ) which is 

 sometimes movably articulated (Bathynomus, Cirolana, Chiridotea), 

 and which bears one or more coupling-hooks (c) interlocking with 

 those of the opposite side. The endopodite or palp consists, in 

 the typical case, of five more or less lamellar segments, but the 

 number is often reduced. In the ovigerous females of Asellus and 

 of certain genera of Valvifera the coxopodite bears a small lappet, 

 fringed with setae, projecting backwards into the marsupium and 



A. 



e P. 



'1. 



lam'A 



FIG. 1-20. 



Mouth-parts of variotts Isopoda. A, mandible of Cirolana boreaHs. B, maxillula-of Chiridotfa 

 entomon. C, maxilla of same. D, maxilliped of same. E, maxilliped of adult female ofRocinela 

 danmonietitiis. F, maxilliped of adult male of same, c, coupling-spine ; ep, epipodite ; i, incisor 

 process ; /I, 7'-', 73, N, endites of successive segments of the appendages (according to Hanson's 

 later interpretation the endites 73, 7* of the maxillula result from the division of a single endite) ; 

 7am 1 - 2 , laminar outgrowths of first and second segments of maxilliped ; m, molar process ; p, 

 palp; s, lacinia mobilis and spine-row of mandible, which in this case are closely associated 

 together; 1, 2, 3, successive segments of the appendages. (After Hausen.) 



resembling the coxal appendage of the second thoracic limb in the 

 females of Cumacea. A similar plate, more largely developed, is 

 found in the females of Cymothoidae (Fig. 120, E) and Epicaridea 

 and of some genera of Sphaeromidae, where it is associated with 

 an expansion of the basipodite and with the epipodite, giving a 

 lamellar character to the whole appendage. In all these cases the 

 vibratory motions of the maxilliped cause a current of water to 

 pass through the marsupium for the aeration of the developing 

 embryos. A similar expansion of the basipodite united with the 

 epipodite occurs also in Serolis, where, however, the coxal lobe is 

 not developed. The position of this coxal lobe and its occurrence 



