D. C. McIntosii 



465 



ceiitn^ ot' tlie sidcs ot' tlic; jH'iitagoii, ;is in Vi^r. ."!. Tho last two coliiiiuis of thc 

 table give tlie percentagc^s of spcciniuns with puiitagonal aiul with circuiar discs, 

 and it will be reniarkud that the uuiiiburs f'or T, are somowhat diffcrcnt f'roni thosc 

 for T„ and T3, which are as consistent with each other as miglit fairly be expccted. 

 But it must be reniembered that the shape of thu disc necessarily depends largely 

 on the ijuantity of food and water in the stomach of the anirnal at any particular 

 time, and that T^ were examined innnediately after being killed, whereas the 

 others had been lying for some time in aleohol. Further, T", consisted of "a<lidt.s" 

 only; and further still, one eft'ect of the alcoliol used for T„ and T-j was to slightly 

 shrivel up the onter coating of the disc and thus better roveal its natural shape. 

 It is clear, thcn, tliat if these tiiree thousand specimens takon at r:niclciin he i'eally 

 typical of Ophiocoma nigra, (1) the shape of the disc is in genural pentagonal, and 

 (2) the disc tends to beconie circuiar in the more fully developed auinials. 



2. ^.s to cülour-rnarkings. 



Th<,'re can be no doubt as to tiie prevailing colour of the speciniens I handled : 

 it is dark brown. Whatever colour-variation oceurred consisted mainly in the disc 

 having a central yellowish sand-coloured patch, and in the rays being occasionally 

 of a lighter brown than the disc. Jeffrey Bell says the colour of this species is 

 " black or dark brown, the arms lighter than the disc ; .sometiines lighter and 

 sometimes spotted." Forbes says: "Müllers name* well applies to the usual 

 colour of this Brittle-star : the disc and rays are comnionly black, or brownish 

 black ; the ray-spines dusky white or bluish. Sometimes the disc is prettily 

 variegated, and there is a variety of an orange colour not uncommon in the Irish 

 Sea. Mr Goodsir and I found some specimens in Shetland, of a niost beautifui, 

 delicate rose colour." Gosse, who nierely describes the single specimen he chanced 

 to find, remarks-f" of the species that "its hues are said to be various." 



Paying no attention to the shape of the disc, but noting only the shape of the 

 coloured patch (if any), I attempted to tabulate the different shape of coloured 

 patches — See Table IL If any colour-marking oceurred at all it was found to be 



TABLE IL 



Showing Relative Size and Shape of Colour-Markings an Disc. 



* The name O. F. Müller uses for this species is Asterias itiyru, while Edward Forbes calls it 

 Ophiiicuntii <ifaititl(ita. 



t A Ycar at the Slmre (Loudon, 1870), P. H. Gosse, p. 2-27. 



