POLYCH^TA SEDENTARIA OF THE FIRTH OF FORTH. 667 



One of the most peculiar features of the genus is the entire absence of 



uncini or uncinigerous tori, that is of neuropoclial elements, in the 13 somites 



which bear the capillary setae. Behind the 13th somite, small uncinigerous tori 



only are present : the uncini are small, uniserial, with two small teeth on the 



dorsal end. 



This worm is of yellowish-white colour when alive, and is somewhat 

 transparent. It writhes when placed in clean water into complicated contor- 

 tions. The anterior region is swollen, the rest of the body cylindrical. 



Subf. Canephoridea. 

 One branchia divided distally into 4 comb-like processes. 



Terebellides Strcemi, Sars. 



Terebellides Strcemi, Sars., Beskriv. og Jakttag., p. 48; Malmgren, 

 Nordiska Hafs-Annulater, p. 396 ; M'Intosh, Fauna of St Andrews. 



Dredged 1 mile from Isle of May ; N.W. of Inchkeith, 13 to 16 fathoms, on 

 muddy ground. We have never found the species on the shore. It is 

 evidently restricted to muddy ground at depths of over 10 fathoms. M'Intosh 

 found large specimens in stomachs of cod and haddock. Malmgren gives as 

 its distribution Spitzbergen, Greenland, Iceland, Scandinavia, Britain, Baltic 

 Sea, and, according to Grube, the Adriatic Sea, on muddy ground, 10 to 250 

 fathoms depth, everywhere rather abundant. 



This form is peculiar among the Terebellidae ; it is the only species of the 

 genus, and Malmgren places the genus by itself in a separate subfamily, the 

 Canephoridea. 



The prostomium is membranous and flexible, the edge being sinuously 

 plicate, and bearing the numerous short thin tentacles at its edge dorsally. The 

 ventral part of the buccal somite is enlarged, and the dorsal contracted, so that 

 the mouth is thrown to the dorsal side, and the end of the body appears trun- 

 cated. The ventral part of the buccal somite carries a transverse membranous 

 projection or crest. There is one single branchia attached to the 1st setigerous 

 somite ; the structure of this is unlike that of any other branchiae in the family. 

 It consists of a peduncle transversely flattened, which bears four pectini- 

 form processes, in two pairs, the anterior pair being much larger than the 

 posterior, and overlapping them. Each process is formed by a stem running 

 backwards and bearing on its upper side a series of thin laminae semicircular in 

 shape. The laminae are placed transversely to the axis of the stem and to the 

 longitudinal axis of the worm, and are so closely crowded together that the 

 branchia seems, on a cursory examination, solid. The stem of the posterior pec- 

 tinate process is of a conspicuous opaque white colour. There are notopodial 



VOL. XXXIII. PART III. 5 E 



