attains three inches in length, is of a yellow colour, with the mantle covered with small round warts. Hence in size, form, hue, and surface, the animal bears no small resemblance to the half of a lemon cut through lengthways, especially when the branchial plumes and the dorsal tentacles are concealed by being withdrawn into their respective cavities. But the colour is not always plain yellow; it sometimes verges to grey, and is frequently marked in the most beautiful manner with large spots and clouds of crimson or purple. The branchial flower is composed of eight plumes, which are large, tripinnate, and of a bluish white hue.
This species is said to be more common on the east coast of Scotland and England than on the west. I have, however, found it on the shores of Dorset and of north and south Devon; it lives among the rocks, in the zone bounded by the limits of high and low tide, as well as in deep water. In captivity, the habit of this, as of some other species of the genus, is to glide slowly round and round the vessel in which it is kept, just beneath