XXXVI. THE FAUNA OF BRACKISH 



PONDS AT PORT CANNING, 



I,OWER BBNGAIv. 



Part XII. — Description of a new species of Poi^ych.^te 

 Worm of the Genus Spio. 



By A. WiLivEY, D.Sc, F.R.S., Director, Colombo Museum. 



Splo bengalensis , sp. nov. 



Amongst the invertebrate animals collected in 1907 by Dr. 

 Nelson Annandale from brackish ponds at Port Canning in Lower 

 Bengal, there were some small tubicolous Polychaete worms which 

 he sent to me for description. Although clearly belonging to the 

 family Spionidse, there appeared, under ordinary inspection, to 

 be no trace of the long occipital (peristomial) tentacles which are 

 characteristic of this family, nor were they seen in the living worms. 

 But after repeated examination under strong reflected sunlight 

 I have found what I take to be the bases or scars of the lost ten- 

 tacles. In its general characters the species otherwise resembles 

 the Spio filicornis described and figured by Malmgren {Annulata 

 Polychceta, 1867, p. 92, pi. i, fig. i) except that th^ branchiae or 

 branchial cirri, instead of occurring on all setigerous segments, are 

 confined to the anterior region of the body, this being the distinc- 

 tive character of the species. 



Fig. I. ■ Fig. 2. 



Fig. I. — Head of Spio bengalensis : p.= proboscis ; /, = tentacular basis. 

 ,, 2. — -Anterior end of Spio bengalensis in side view. 



The material includes at least two mature females ; the ovaries 

 commence in the posterior branchial region and may be followed 

 segmentally on each side of the gut to the hinder region of the 

 body. The size is small, 12 to 13 millimetres in length, with about 

 70 segments. 



The four small eyes are placed as shown in fig. i when the 

 proboscis is protruded, but the ocular area becomes narrower 

 when the proboscis is withdrawn. The prostomium is slightly 

 emarginate in front ; behind the eyes it narrows down to a pointed 



