6i6 Memoirs of the Indian Museum. [Voi,. V, 



4 



different localities they would probably have been regarded as distinct species. It 

 seems very probable, however, that the distinctions observed are due to differences in 

 size and age. The most important difference is in the relative lengths of the branchia 

 and dorsal cirrus, and it is difficult to see how this can be a function of age and size. 

 The large specimens were found only at one locality, in March, though empty tubes, 

 apparently belonging to this form, were obtained in September. The small specimens 

 were found both in March and September. The question of whether one or two 

 species are involved can only be decided by a more ample supply of material, collect- 

 ed at different seasons of the year. 



If all the specimens are regarded as belonging to the same species, then the follow- 

 ing variations were observed : — 



i. In the anterior segments the dorsal cirrus may be longer than, equal to, or 

 only one quarter as long as, the stem of the branchia. 



2. The branchiae may commence on the 4th or 5th foot. 



3. The branchial filaments may be long and open, or short, and bushy. 



4. The stem of the branchia may be thick or thin, and the base may be clearly 

 or obscurely ringed. 



5. There may be few or many branchiae pairs of (33-120), according to the size 

 of the individual. 



6. There may be few or many feet with simple branchiae. 



7. The peristomium may or may not project over the posterior part of the head. 



8. There may be considerable variation in the number of teeth in the dental 

 plates. 



These variations show that many of the criteria which have hitherto been used 

 to discriminate the various species of this genus, are of little or no value. Crossland 

 (1903, p. 132) has already commented on this point. In these circumstances it is 

 probably useless to compare the present species with the majority of the species 

 previously described, which will need careful examination, and will probably be con- 

 siderably reduced in number. The most characteristic features of this species are the 

 long dorsal cirri (in the large specimens), and the shape of the dorsal serrate capillary 

 setae in the middle and posterior segments. In the possession of long dorsal cirri, 

 the species agrees with D. amoena, described by Kinberg (1910, p. 38), from the 

 Atlantic, near the mouth of the Rio de la Plata. The text is too brief to be of any 

 value, but judging from the figures recently published, D. amoena differs from the 

 present species in having smaller, and probably fewer branchiae, with fewer fila- 

 ments, more elongate feet and larger palps. The upper jaws also differ in shape, 

 especially the supports and forcipate processes. 



The smaller specimens, however, closely resemble certain species already des- 

 cribed, such as D. chiliensis, Quat. (Ehlers 1901, p. 123), and D. leuckarti, Kinberg 

 (1910, p. 38). The structure of the dorsal capillary setae, which apparently differen- 

 tiates the present species, may have been overlooked by previous workers. 



Habitat. —Dr. Annandale writes of the large specimens of this species — " I think 

 it is the largest worm in the collection. Specimens were taken in February or March 



