224 SIPHONOSTOMACEiE. 



filiform tentacula-like branchiae, the whole entirely retractile : mouth 

 terminal : bristles of the anterior rings elongated, porrect, concealing 

 the branchiae more or less : feet alike, with simple dissimilar bristles 

 on both branches : anus terminal and simple. 



The Trophonia has a short membranous retractile proboscis fur- 

 nished with two tentacula and eight filaments, which are supposed 

 to be branchial. They are naturally flesh-coloured ; but they often 

 become of a bright grass-green, from the blood being forced into 

 them by the motions or will of the creature. It can also inject this 

 green blood into the tentacula, but, from their denser structure, they 

 do not become thoroughly coloured by it. The tentacula are thicker 

 than the branchial filaments, and somewhat annulated ; and they are 

 capable of being extended considerably beyond them. 



The anterior portion of the worm is often bulged like that of the 

 Arenicola. Its resemblance, both in outward figure and in motions, 

 and in mutability of shape, to a Holothuriuy e. g. to the Holothuria 

 inhcerens of Miiller, is very remarkable. It was this resemblance 

 that misled me first to describe the genus as a member of the family 

 Siphunculidce. 



1 . T. plumosa, body somewhat hispid, with about from fifty to sixty 

 segments, granulous ; bristles of the first three segments long and 

 porrect ; branchial filaments four on each side in two rows. Length 

 2-4" ; breadth 3-5'". Plate XIX. figs. 1-10. 



Amphitrite plumosa, Mull. Zool. Dan. Prod. no. 2621. Fabric. Faun. 



Groenl. 288. Mull. Zool. Dan. iii. 16. tab. 90. f. 1, 2. Turt. Gmel. 



iv. 83. 

 Pherusa Miilleri, Blainv. Diet, des Sc. nat. Ivii. 440. Quatrefages in 



Ann. cit. 291. 

 Flemingia muricata, Johnston in Trans. Berw. N. Club, i. 15 (1832). 

 Flemingia plumosa, Johnston in Ann. Sf Mag. N. Hist. xvi. 447. 

 Trophonia Goodsirii, Johnston in Ann. Nat. Hist. ix. 37 1. pl.ll.i. 1-10. 



W. Thompson in ibid. xiii. 437. Johnston in ibid. xvii. 294. 

 Siphonostoma plumosum, Rathke in Nov. Act. Acad. Nat. Cur. 1843, 



XX. 208. tab. 11. f. 1, 2. Ray Soc. Rep. 1845, 283; and 1847, 



508. 

 Pherusa Goodsiri, Quatrefages in Ann. des Sc. nat. xii. 290 (1849). 

 Siphonostomum plumosum, Grube, Fam. Annel. 73. 



Hab. The laminarian and coralline regions. 



Desc. Worm from 3 to 4 inches long, as thick as a swan's quill, 

 distinctly annulated, tapering insensibly backwards to an obtuse 

 point, subcylindrical, but so flaccid after maceration in spirits that 

 the sides almost fall together, of a uniform earthy-brown colour or 

 bluish underneath, rough with numerous granulations, which are 

 somewhat larger on the dorsal than on the plane ventral surface. 

 The cuticle or outer skin is easily separable from the body, which 

 then appears of a dull leaden-blue colour, more or less iridescent. 



