236 ILYANTHIDJS. 



of them are bifid ; the back lobes have a tendency to be simple, except the 

 central back one, which is large, and composed of two bifid ones united 

 on a single stem ; this compound one is generally bent over as a protection 

 to the orifice of the gonidial tube. The papillaj resemble tentacles in that 

 they are hollow, with thick walls, the internal surface of which is lined 

 with brown pigment, deepening at the tips ; they are very moveable. 



Colour. 



Column. Pale red or flesh-colour, through which the edges of the 

 septa appear as twelve white lines : the fore half of the column is fre- 

 quently marked with irregular splashes of chocolate-brown, which are 

 sometimes confluent. 



Dish. Pale red or buff, each radius marked with two Vs of deep 

 brown, one within the other, the points of which are outwards; the point 

 of the outer one meets the tentacle, and sends off a branch on each side, 

 encompassing its foot. 



Tentacles. Pellucid, each marked on its front face with arrow-heads of 

 deep brown, arranged in two longitudinal rows, the points downwards ; 

 there are about six in each row, but near the tip they become indistinct. 

 Each arrow-head is separated from its successor by one of opaque cream 

 colour or pale sulphur-yellow. 



Mouth. White, with the furrows deep brown. 



Conchula. Pale salmon-colour; the lobes pellucid, with an opaque 

 white core, which is crossed by a brown bar near the tip. 



Size. 



About four inches in length, and one in greatest diameter. I have seen 

 the body lengthened to eight inches, without any signal attenuation. 



Locality. 

 Turbay, at extreme low water, and thence downward, buried in sand. 



In a paper read before the Linnean Society on the 20th 

 of March, 1S55, I characterised this genus and species 

 from specimens presented to me by the Rev. Charles 

 Kingsley. I named it after Mr. Charles W. Peach, who 

 was the discoverer of the first British Ilyanthidan known, 

 which I at that time referred to the same genus. In June, 

 1856, MM. Danielssen and Koren founded, on a species 

 occurring on the coast of Norway, their genus Siphon- 

 actinia, which is evidently identical with this, though 

 they appear to have mistaken the conchula for the mouth. 



