246 TEREBELLID^. 



The number of segments, and their structure, appear to be the same ; 

 but the abdominal portion has a pointed end, which covers, Hke a 

 flap, the anal aperture. There is a great similarity in the colour 

 and form of the cephalic spines, and of the bristles of the feet. 

 There are about thirteen spines in each frontal fan. The inferior 

 lobe of the foot becomes more developed on the posterior segments, 

 and assumes the form of a triangular auricle, on the margin of which 

 the uncini or booklets are inserted like a neat edging. There is a 

 small papilla on the dorsiim of the caudal flap. — The tube resembles 

 the Dentalium entails in size and figure. It is usually about 2" 

 long, as large at the superior aperture as a small goose-quill, tapered 

 backwards to a point, and slightly curved, arenaceous and brittle, 

 the surface even, with the grains of sand so joined together as to give 

 them an areolated appearance, 

 (a) Berwick Bay, Di'. Johnston. 



I had included Amphiti'ite auricoma of O. Fabricius in my syn- 

 onymy of this species before I possessed the " Famihen der Anne- 

 liden" of Dr. A. E. Grube, on whose authority I now keep them 

 separate. The third species is also, probably, native to our seas ; 

 and it may be useful to append Grube' s specific characters : — 



1 . P. belgica, body gradually narrowed backwards, with all the seg- 

 ments short ; frontal edge of the head with 60 or more tentacular 

 papillae ; tentacula about 20 on each side ; bristles of the front 1 5 

 on each side ; oral veil not separated from the opercular segment 

 by a stricture ; hinder margin of the dorsal plate of the opercular 

 segment entire. 



2. P. granulata, body gradually narrowed backwards, with all the 

 segments short ; frontal edge of the head with 24-28 papillae ; 

 tentacula 16 on each side ; bristles of the front 13-16 on each side, 

 acute ; oral veil not separated from the opercular segment by a 

 stricture ; hinder margin of the dorsal plate of the opercular seg- 

 ment with about 14 denticulatious. 



3. P. grcenlandica, body gradually narrowed backwards, with all the 

 segments short ; frontal edge of the head with about 46 clavate 

 filaments ; tentacula about 60 on each side ; bristles of the front 

 9-10 on each side ; oral veil not separated from the opercular seg- 

 ment by a stricture ; hinder margin of the dorsal plate of the oper- 

 cular segment entire. 



and the whole is liued with the slightest silken coating. The sand being col- 

 lected at the orifice of the tu1)e, its tenant, chiefly by means of the tentacular 

 organs, selects those which arc ai)propriate, and applies them to use. Tliis is 

 done only through the night, all the additions being made at the orifice, and as 

 the animal grows, the sha])e and dimensions of the tube, being an inverted conic 

 frustum, result from the successive growth of the body," — Dalyell. 



