THELACHROS RHIZOPHORA. 55] 
Thelaceros rhizophore, n,g. et sp., 
an Actinian from Celebes. 
By 
P. Chalmers Mitchell, B.A., 
Junior Demonstrator in the Morphological Laboratory, and Assistant to the 
Linacre Professor in the University of Oxford. 
With Plate XXXVI. 
Tus beautiful Actinian was obtained by Dr. Hickson in a 
mangrove swamp in Celebes, and he was good enough to give 
it to me to describe. Owing to the strong contraction of the 
mesenteries the tissues within the column were very badly pre- 
served, and were exceedingly brittle. As there was only one 
specimen, a part containing one pair of directive mesenteries 
was not dissected. I am, therefore, far from being able to 
give a complete account of the anatomy of this form, but I 
believe that I have made out its leading features. 
External Characters.—Dr. Hickson has given me the 
following notes concerning the discovery of the specimen, and 
its shape and colour when alive :—‘ I found this Actinian in a 
few inches of water, by the side of one of the roots of a 
Rhizophora tree near the shore side of the mangrove swamp 
in Talisse Island, N. Celebes. There were three or four others 
in the immediate neighbourhood, but this was the only speci- 
men I obtained. At first I thought the anemone was actually 
attached to the root by its pedal disc, but when I attempted to 
take it, it rapidly burrowed in the sand and disappeared 
from view. Failing to secure the specimen by searching for it 
