350 PERCY SLADEN TEUST EXPEDITIOX. 



in others, outer border only ciliate, and tubercles confined to small area of surface 

 (var. glabra, fig. 22). 



Ventral setie with following succession : — 



(1) Spinose simple setae ; (2) slender type of compound seta, with long jointed 

 appendix and spinose shaft ; (3) stronger setae with smooth shaft and short appendix ; 

 (4) slender setae with smooth shaft and long jointed appendix. 



In first few segments all setae elongated, with long jointed appendices (Hulule, Male), 

 and setae of type (2) are absent. 



Localities : — 



Var. hirsuta. (1) Hulule, Male Atoll, Maldives ; fragment measuring 28 mm. in length 

 and 4 mm. in breadth ; another fragment occun'ing with Thalanessa digitata. 

 (2) Wasin, Zanzibar ; dark-coloured and smaller. 



Var. glabra. (1) Zanzibar ; complete specimen measuring 37 mm. in length and 3'5 

 mm. wide. (2) Hulule, Male Atoll, Maldives ; fragment, 3 mm. in breadth ; elytra in 

 forms from both localities with a brown spot in centre. 



In this species are grouped a number of slender forms which have some differences 

 among themselves with regard to markings and fimbriation of the elytra, but which 

 resemble each other in the general character of the setae. 



With regard to the variation of the elytra, a more detailed description of the two 

 varieties is given below : — ■ 



(1) Var. hirsuta. In some of the worms from Hulule, Male, the posterior border is 

 provided with cilia as well as the outer margin, though those in the former position are 

 much shorter. Finally, in one the surface of some of the hinder segments is actually 

 invaded by these cilia, posteriorly and externally, and a rather shaggy appearance is 

 thus given to the elytron. It is easily seen that the small rounded tubercles which 

 here entirely cover the surface really are the initial stage in the development of tlie 

 cilia. This variety, then, is characterised by the marked development of the cilia. 



(2) Var. glabra. In the specimen from Zanzibar and one of those from Hulule, Male, 

 only the outer border is ciliate, though the cilia are ratlier longer. In addition, the 

 tubercles, which cover the whole of the surface in the above described variety, are here 

 generally absent from the surface, except round the concavity of the anterior margin 

 and a small patch on the internal angle. In the first three elytra the surface is 

 completely covered by the tubercles. Moreover, they depart from the rounded 

 character, which they possess in all the other segments, and become blunt spines. 

 This development was noted especially in the internal part of the elytra of the Zanzibar 

 specimen. 



The characters of the sette, which distinguish all members of the species, is the 

 possession of upper ventral setae of a spinose character, which are often simple, but 

 tend to be modified into compound setae with long serrate appendages. These latter 

 always possess spinous shafts. The relation is very variable, for occasionally one of the 

 forms would occur to the exclusion of the other, but no fixed rule could be made out 

 with regard to this. 



