32G 



CEYLON PEAEL OYSTEE REPORT. 



Each parapodium of the 7th and following segments bears two or three hooded 

 ventral uncinigerous setae. The general outline of the worm is noticeable. The 

 caruncle is slightly bilobed in front and extends backwards to about the 2nd 



/! 



Polydora armata, Lnghs. Posterior part in dorsal 

 view, x 75 ; part of a dorsal posterior fascicle ; 

 and seven dorsal seta? from a posterior fascicle, 

 x 375. 



setigerous segment : the anterior ten or 

 eleven segments (except the 5th) are 

 nearly equal to one another in length and 

 breadth ; they are followed by seven or 

 eight segments, which are much larger, 

 being nearly double the length and 

 breadth of the former ; in the hinder 

 part of the worm the proportions of the 

 segments become somewhat similar to 

 those at the anterior end. The anal 

 segment is broader than the preanal (see 

 fig. in text). It is somewhat reniform 

 in outline, the indent being dorsal. The 

 segmental divisions in the anterior part, 

 although fairly clear, are not deep, but 

 commencing with about the 13th seti- 

 gerous segment the separation becomes more and more distinct, until the last four or 

 five preanal segments, in which it is very marked. This marked separation is further 

 accentuated by the presence in the parapodia of these last segments of a fascicle of 

 from 15 to 18 stout brown setae, which vary greatly in form, size and proportion, 

 a fact which was not shown by Mesnil. The forms comprised are acicular, lanceolate 

 and scimitar-like (see tig. in text). 



These setae, which are more numerous than in Mesntl's examples, have usually 

 their points drawn together in preserved specimens, forming a hollow, subspiral, 

 truncate cone ; but in several cases I have found the fascicle opened out, the points 

 of the setae being widely directed outwards, an arrangement extending over three 

 parts of a circle, the central convexity of which is directed antero-laterally. By 

 dissection the fascicle can be unrolled, when the setae of which it is composed are seen 

 to be arranged symmetrically side by side, the longest in the centre and the smallest 

 at the outer edges. Probably in life the fascicle is expanded with a sweeping action. 

 The forms of the setae seem admirably adapted to the function described, the swollen 

 parts, some distance from the base of the seta, doubtless acting as fulcra and 

 rendering mutual support and aid in the action I have suggested. 



The distribution of the species as noted by Mesnil is : Atlantic Ocean (Madeira), 

 Mediterranean (Naples), British Channel (Manche : " Anse St. Martin"), to which we 

 now add the Gulf of Manaar. 



HARRISON AND SONS, PRINTERS IN ORDINARY TO HIS MAJESTY, ST. MARTINS LANE. 



