on the west coast of Ireland. It covered a very large surface of 
rock, growing almost to the exclusion of every other species, both 
in places left bare at low water, and in the small tide-pools. In 
both situations it seemed to prefer the stunted fronds of Coral- 
lina officinalis for its habitat. It has a softer and more gelatinous 
substance than any British Ceramium, and this character, with 
its extreme tenuity, and the minute, fastigiate lateral branchlets, 
readily distinguish it from any of the section of the genus to 
which it belongs. 
On communicating specimens to Professor Kiitzing, he formed 
me that they were identical with his Hormoceras gracilimum — 
described four years previously. There can therefore be no con- 
fusion of synonyms in our adopting the species of the German 
author, whose specimens came from the Adriatic. 
C. gracillimum is the smallest and most slender of our British 
Ceramia. So slender are its threads, so flaccid, and so densely 
crowded together, that it is almost impossible to display them 
properly on paper. ‘They almost invariably become entangled 
together, and once this has occured, it is in vain to attempt their 
disentanglement. 
Fig. 1. Tuft of CrRAMIUM GRACILLIMUM, growing on Corallina officinalis; the 
natural size. 2. Abranch. 3. Aramulus. 4. Pedunculated Favella with 
its involucre ;—all more or less highly magnified. 
