GENERAL MORPHOLOGY 275 



more flexible structure in which first the distal portion of the lamella becomes free from 

 the endite {B') and later from the basis (B) itself. 



For these reasons, in this paper, I shall refer to the " distal portion of the epipodite" 

 (Hansen) as the lamella of the basipodite, and the "proximal portion of the epipodite" 

 as the epipodite proper. 



Beddard (18846, p. 56, pi. iv, fig. 8) and Hodgson (1910, p. 28, pi. iv, fig. 5) describe 

 and figure the maxillipeds of S. bromleyaim, Suhm, and S. trilobitoides, Eights, re- 

 spectively : in both the figures the coxopodite is shown fused with the epipodite. I have 

 examined specimens of these species and find that a suture between the coxopodite and 

 epipodite is clearly visible in each, so that the maxillipeds of all the species of Serolis fall 

 into one or other of the four groups mentioned above. 



The endopodite of the maxilliped of the majority of species of Serolis consists of three 

 joints; in a few species, however, near the extremity of the third joint, at its outer angle, 

 is a fourth small one, the distal extremity of which does not extend beyond that of the 

 third: its truncate extremity bears several long setae. Such a joint is well developed in 

 S. platygaster, n.sp. (Fig. 19 o). This small joint probably represents the fourth joint 

 of the primitive five-jointed endopodite. 



A further point of interest in connection with this limb is the modification in the form 

 of the coxopodite of the female during the breeding phase. In the breeding female there 

 is a very definite increase in the size of the coxopodite as compared with that of the male 

 (Figs. 2 b-e), and this increase is brought about by a thin lamella-like extension of 

 the posterior and inner margins of the joint (C), the distal angle of which is also often 

 produced to form a small lobe. Delicate setae are developed along its inner margins. 



This modification in the form of the coxopodite of Serolis has not been previously 

 noted, and Caiman (1909, p. 199), in dealing with the development of coxal lobes on 

 these joints in ovigerous females of members of the order Isopoda, states that in Serolis 

 no such lobes are developed. Nevertheless, the lamella-like extensions (C) of the 

 coxopodites in the breeding females of Serolids must be regarded as coxal lobes. They 

 are similar in form to the corresponding structures seen, for example, in the ovigerous 

 females of Phreatoicus australis, Chihon, and these are homologous with, though less 

 well developed than the corresponding lobes of the allied species Ph. latipes (Chilton) 

 (see Sheppard, 1927, p. 87, fig. i (4) and p. 90, fig. 2 (i)). 



Beddard (18846, pp. 15-17) gives an account of a number of secondary sexual 

 characters in which the male differs from the female. To these may be added the 

 following : 



(i) In certain species, e.g. S. glacialis, Tattersall, S. kcinpi, n.sp., and S. aspera, 

 n.sp., the number of joints in the flagellum of the antennule is considerably greater in 

 the male than in the female. 



(2) In S. convexa, Cunningham, S. gaudichaiidii, Aud. et Edw., and S. laevis, 

 Richardson, the form of the modified spines on the propodus of the second thoracic 

 appendage shows a sexual variation (for details see the descriptions of the species). 



(3) Long delicate setae are present on the outer margin of the propodus of the second 



