324 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XYI. — On a New Species of Cactogorgia. By Jas. J. Simpson, M.A., 
B.Sc., Carnegie Research Fellow, Natural History Department, 
University of Aberdeen. (With One Plate.) 
(MS. received January 24, 1910. Bead January 24, 1910.) 
Amongst the unnamed Alcyonaria in the collection of the Royal Scottish 
Museum, Edinburgh, is a beautiful colony belonging to the genus Cacto- 
gorgia, which Mr Eagle Clarke has kindly handed me for identification and 
description. 
In 1907 (Trans. Roy. Soc. Edin.) I established the genus Cactogorgia 
for several small colonies from the Indian Ocean, and referred these to three 
separate species, viz. celosioides, alciformis, and expansa. Thomson and 
M‘Kinnon, in Trans. Linn. Soc. ( Zool .), 1909, have described another species 
from the Seychelles under the name of Cactogorgia lampas, and the 
present colony must also be referred to a new species. This we propose to 
name Cactogorgia agariciformis, n. sp., on account of its very definite 
mushroom-shape. 
It is interesting to note that the inclusion of these two new species has 
not necessitated any change in the original generic diagnosis. 
Cactogorgia agariciformis, n. sp. 
This species is represented by a single specimen of a slightly orange- 
yellow colour — that is, after prolonged preservation in alcohol. It has been 
attached to rock, and the basal disc is overgrown by an encrusting sponge. 
The colony (fig. 1) is 7 A cm. in height, and consists of two very distinct 
parts : (1) a lower, almost cylindrical, stalk, 4*8 cm. long, 7 mm. in diameter 
at the base and 12 mm. at the top ; and (2) an upper, polyp-bearing, part, 
elevated in the centre, circular in outline and expanded horizontally, giving 
the whole colony a very distinct mushroom appearance. The breadth of 
the capitulum is 31 mm., and its maximum height 12 mm. 
The whole colony is very stiff and rigid, owing to the densely interlaced, 
large, warty spindles, which are quite visible to the naked eye. These are 
arranged for the most part longitudinally, and give the translucent appear- 
ance which was characteristic of C. celosioides to the whole colony. 
The stalk contains several large canals (fig. 2). These are supported by 
