123 
CPe *ture is at present unknown. The similarity between the 
Ce Hs of this species and the Cellularia avicularia is so very 
| rea l, that many naturalists have considered them the young 
adult state of the same species; and for this, or some other 
eas on, Dr. Fleming in his “ British Animals” ranks them as 
I he refers his F. avicularis to the Grisia avicularia and 
• .flustroides of Lamouroux ; and the Serlularia avicularia 
Linnaeus; this cannot now however, be maintained. As 
e cells in C. avicularia are only in two alternate rows, 
, bile the Flnstra avicularis has about tour or live, the cel- 
i s supposed to be the youngest state. In answer to 
h's, it may be observed, that the Flnstra avicularis has been 
gained only one fourth of an inch in height, yet having the 
| UU|- and five rows of cells; while the Cellularia avicularia 
!l as not been found so small, but almost always higher than 
,' e Flnstra, and sometimes one third as high again with only 
rows of cells ; and they have not yet been found in 
j "ipany with each other. In addition to this, the Flnstra 
} common, while the other is comparatively rare ; and in 
a th the Flustra changes to a brown, while the other fades 
a dull white ; so that there can be no doubt of their being 
v^tinct. This opinion is also entertained by Johnston, 
‘Ine Edwards, and Mr. Bean. 
* * * Crustaceous 
^AGRIN SEA-MAT. F. Membranacea. Encrusting ; 
cells quadrangular, alternate, with a blunt spine at each 
a Bgle. 
lustra membranacea, Ellis and Solander’s Zooph., p. 18, 
- ' 12. Turlon’s Lin., vol. 4, p. 6G5. Fleming’s Brit. An., 
>* **36. Slewart’s Elem., vol. 2, p. 437. Johnston’s Brit, 
p. 287, pi. 38, fig. I, 2, 3. 
»o, 
Co 
Hub. On seaweed, ( Laminaria digitata) every where 
" ,r "on. PI. xxi. 
j This abundant species, encrusts the broad fronds of the 
^Ser sea weed, in spots varying from a mere speck to two 
a r l hree feet in length. It has a very delicate and gauze-like 
J'Pearance, and while lying exposed on the shore looks more 
n ® a thin saline incrustation, than a living being. On ex- 
c“ llna tion even with the naked eye, it will be found to be 
.exposed of quadrangular cells, with a blunt horn on each 
g'Sle. The longest diameter of the cell is in the axis of 
p o 0 *th, ant j the rims only are calcareously white; the other 
p l tions being white and translucent. On the upper or distal 
^ le ce ^> and but a very short distance from the two 
is a small semi-lunar" opening, convex above and 
