BRISSOPSIS. 173 



p. 597 ; Al. Ag. Rev. Ech. (1872) pp. 95 & 354 ; Mob. fy Biltsch. 

 JB. Coram. Kiel, ii. & iii. (1875) p. 150 ; Ludicig, Mitth. zool. Stat. 

 Neap. i. (1879) p. 562 ; AL Ag. Mem. Mus. C. Z. x. 1. (1883) p. 69 ; 

 Koehler, Ann. Mus. Marseille, i. 3. (1883) p. 135 ; Cams, Prod. 

 Faun. Mediter. (1884) p. 103 ; Rathbun, Proc. U.S. Nat. Mus. ix. 

 (1886) p. 289 ; Hoyle, J. Linn. Soc. xx. (1890) p. 458 ; Scott, Rep. 

 Scot. Fishery Board, 1889 (1890), p. 316 ; id. Ann. Scot. Nat. Hist. 

 1892, p. 50. 

 Brissiopsis lyrifera, Gray, Brit. Rad. (1848) p. 7; id. Cat. Ech. 

 (1855) p. 55. 



This species may be at once recognized by the lyre- or fiddle- 

 shaped black fasciole on the dorsal surface. 



Body elongated or more or less oval, rather higher posteriorly 

 than anteriorly ; pretty closely covered with rather short and 

 delicate, slightly curved spines, which are longest and strongest on 

 the edges of the ambulacral petals and just in front of the mouth. 

 The general co]oration is brown, but the spines are light yellow ; 

 the finer spines of the peripetalar and of the subanal fascioles are 

 very much darker. 



The peripetalar fasciole varies a good deal in the details of its 

 course, but its general direction is as follows : there is a band at 

 right angles to the anterior odd ambulacrum, placed at the point 

 where the test begins to sheer downwards ; on either side it takes a 

 more or less angulated course to the tips of the antero-lateral petals ; 

 the band then curves inwards, sweeps outwards around the postero- 

 lateral petals of either side, and joins its fellow in a nearly straight 

 transverse band. The subanal fasciole, which is of a transversely 

 elongated oval form, varies somewhat in the extent of its distinct- 

 ness ; the spines within it are disposed in two diverging tufts, but 

 are not prominent as in Spatangus purpureus. 



The tubercles on the test are rather coarse, and are coarsest 

 below and anteriorly, and are nowhere very closely packed. The 

 part within the peripetalar fasciole is longer for the antero-lateral 

 than for the postero-lateral ambulacra, and the former are also 

 somewhat more deeply excavated. The madreporite, which lies 

 between the proximal ends of the latter, is rather small and very 

 finely punctured. The lower lip is hardly at all curved from side 

 to side or from above downwards. The periproct is irregularly oval 

 in form and its somewhat longer axis is vertical; the outermost or 

 peripheral plates are of some size. When the spines are particularly 

 well-developed the peripetalar fasciole is a good deal obscured, the 

 spines within the two fascioles become much more prominent, and 

 those below much longer than ordinary. 



A great quantity of mud becomes entangled in the spines of this 

 species. 



Height. Peristome. Periproct. 



29 11-3 



31 10 6 



33 10 7 



23 6 4 



21 5 



