STHENELAIS BOA. 409 



more slender forms, with a few rows of spines on the slightly expanded distal regions of 

 the shafts, and an appendage of one to four joints. A group of long papillae occurs at 

 the anterior edge of the superior division, one above the spine of the ventral division, 

 and a ciliated or papillose frill is found at the base of the lowest slender bristles. Yentral 

 cirrus elongate, subulate, barely reaching the tip of the fleshy part of the foot. 



Synonyms. 



1833. Sigalion boa, Johnston. Loud. Mag. Nat. Hist., vi, 322, f. 42. 



1839. „ „ idem. Ann. Nat. Hist., ii, 439, pi. xxiii, f. 6—15. 



1843. „ Idunse, H. Rathke. Nova Act. Acad. Cassar. Nat. Cur., xx, 150, Tab. ix, f. 1—8. 



1851. „ „ G-ruhe. Fam. Annel., p. 38. 



n ,, boa, Williams. Eept. Brit. Assoc, 1851, p. 201. 



„ „ Idunse, Sars. Nyt. Mag. Natur., xi, 3, p. 254. 



1861. „ „ idem. Yid. Selsk. Forh., 1861, p. 1 (sep. copy). 



1865. „ „ Malmgren. Nord. Hafs.-Ann., p. 86. 



„ Sthenelais I.dunse and S. boa, De Quatrefages. Ann., i, p. 276. 



„ Sigalion boa, Johnston. Cat. Brit. Mus., 124, pi. 13, f. 6. 

 1867. „ „ Parfitt. Annel. Devon., p. 19. 



1873. Sthenelais Idunse, Sars. Bid. Christ. Faun., p. 14. 



„ Sigalion Idunse, Willemoes-Suhm. Zeit. f . w. Zool., xxii, p. 347. 



1875. „ „ Ehlers. Annel. ' Porcupine/! 869, op. cit., p. 18. 



1876. Sthenelais boa, Mcintosh. Trans. Zool. Soc, ix, p. 390. 



1879. Sigalion Idunse, Tauber. Ann.. Danic, 83. 



1880. Sthenelais Idunse, Langerhans. Zeit. f. w. Zool., xxxiii, p. 276, Taf. xiv, f. 6. 



1883. Sigalion Idunse, Levinsen. Nord. Annul., 199. 



1884. „ „ V. Cams. Faun. Medit., p. 205. 



1888. Sthenelais Idunse, De St. -Joseph. Ann. d. Sc. Nat. (7), v, p. 187, pi. viii, £. 55. 



1890. Sigalion Idunse, Malaquin. Ann. Boulon., p. 23. 



1891. „ boa, Hornell. Op. cit., p. 238. 



Habitat. — Eanges from Shetland to the Channel Islands, being procured by the 

 dredge in the former and between tide-marks in the latter. It appears to be a generally 

 distributed species, frequenting both shores of Ireland, and extending to Norway and 

 Sweden. Ehlers gives a depth of 60 to 80 fathoms in the Minch during the ' Porcupine ' 

 Expedition of 1869. Shores of France. 



Read (Plate XXIX, fig. 1) of a fine crimson hue, somewhat broadly ovate, and 

 separated from the body by a nuchal collar. Anteriorly a median ridge terminates in 

 the broad basal process for the pale median tentacle, which is comparatively short. At 

 the sides of the basal process (ceratophore) are a pair of flap-like organs (ctenidia), the 

 anterior being the longer, the posterior the shorter. Both are rather flattened, and move 

 freely with the broad tentacular base (first foot) on the head— which is fixed. At their 

 base externally on each side are the eyes, the anterior and larger pair of which are almost 

 hidden under these processes— when viewed from the dorsum, especially as they are also 

 placed on the front of the head so as to look forward and outward. The posterior pair 

 lie a little behind their bases on the dorsum. At the posterior border on each side is a 

 well-marked process or papilla with a truncated tip (one of the " organes nucaux "). The 



