122 
This delicate species grows to the height of one third of 3,1 
inch, and is of a light straw colour ; the cells are on both 
sides, running from the base to the apex, are quadrangular 
form, but enlarged about the centres. It is dichotomously 
branched, and the terminations of the branches are ax®' 
shaped, or truncated. 
Fleming seems to be in doubt, whether to consider tb' 9 
as a distinct species, or a variety of the preceding; b® 
founds bis doubts on a specimen sent him by Montagu; bid 
the specimens I have seen do not countenance such a doubt" 
It much more resembles the Flustra truncata; from which 
there appears to be no sure mark of distiction. 
* * Foliaceous, with cells on one side only. 
FAN SHAPED SEA-MAT. F. Avicularis. Cells quad' 
rarigular, in three or four rows, with a spine at each dist* 
angle on the external edge, and one on each side belo&i 
pointing across the cells. 
Ellis’ Coral., pi. 38, fig. 7. Flustra avicularis, Fleming^ 
Brit. An., p. 536, no. 14t. Crisia flustroides, LamourouX s 
Cor. Flex., p. 141. Johnston’s Brit. Zooph., p. 286, pi. Sft 
figs. 3, 4. 
Ifab. On stones, shells, especially the Pinna ingens a®^ 
Pecten maximus, on the hack of the larger spider crab®* 
from deep water; common. 
This very beautiful and delicate species varies in height 
one inch, it is however sometimes so small as not to excc e 
one filth of an inch ; when living it is of a very delink 0 
flesh colour, but in dying it changes to a dull brown. 
The polypidoni is compressed, thin and divided dicb°J 
tomously into flat segments which terminate in a truncal 6 , 
manner; when living it is very elastic, but when dead it lS 
so friable that it falls to pieces on the slightest bandli®<>' 
The cells are on one surface only of the polypidom, tb e 
other being plain or marked only by the attachments of l *‘ 6 
bases of tbe cells. They are quadrangular in form, and at® 
arranged into from three to five alternate rows. The sU 
perior and external margins have a single stout spiue, one ° n 
each angle, between which rises a pearly globular opercul u,I) ' 
Interiorly to these are two other spines, which pass t rall . s 
versely across the diameter of the cell, reaching neai n/ 
about the middle. On the external margins of the c ® 
there is frequently to be observed, a very curious and 
markable appendage in tbe shape of a bird’s bead. Wl> 6 
the specimen is living this organ is continually employ od 1 
opening and closing its bill ; but of what service it is t° tB 
