Pherusa. 
Z. ASCID10IDA. 
271 
Coast of Devonshire, Dr Coldstream. Stevenston, Ayrshire, 
JRev. D. Landsborough. 
“ Breadth nearly an inch, hispid ; the cells seem distributed over 
the whole surface, and more vertical than the preceding ( Tub. pati- 
na) ; there are, however, waved porous grooves, and the cells seem 
disposed on each side of these in irregular transverse rows, united or 
free, short, with expanding orifices dividing into irregular spinous pro- 
cesses.” Fleming. — I have two specimens of a polypidom, given to me 
by Dr Coldstream, which agree very well with this description, and are 
figured in the plate referred to, but they adhere to a piece of sand- 
stone, and were found in situ at low-water mark. The crust is half 
an inch or a little more in diameter, arid scarcely a line in thickness, 
circumscribed by the thin very narrow edge of the basilar layer. It 
is hard, calcareous, entirely adherent, of a greyish white colour, with 
lighter slightly elevated roundish spots on the surface, or raised into 
transverse ridges, conforming in this respect, perhaps, to the form of 
the rock over which it spreads. The cells are barely visible with the 
naked eye, erect, very close or coalescent, and not arranged distinct- 
ly in any order. Their apertures are even with, or raised somewhat 
above, the surface, circular, and armed on one side with three small 
teeth, of which the central one is larger than the other. Many of 
the cells are destitute of these, which are only perceptible when the 
polypidom is viewed obliquely. 
The genus Discopora differs from Tubulipora in having cells in such 
close and intimate union that they seem almost to be rather immersed 
or excavated in the crust than separate tubes ; while from Lepralia 
it estranges itself by the erect position of its cells, their tubular form 
and non-constricted aperture, which, moreover, are at no season closed 
with ovaries. The British species answers so well to Lamarck' s 
definition of Discopora verrucosa, Anim. s. Vert. ii. 165 ; Stark , 
Elem. ii. 436 ; that at one time I had concluded their identity to be 
scarcely doubtful, but Blainville’s figure (if correct) of the latter 
proves the contrary, and represents a species with oblique ventricose 
cells, similar in all apparent respects to those of a Lepralia, The fi- 
gures I give of the natural size are very exact to nature, — that drawn 
under the microscope is perhaps less characteristic, but there was no 
possibility of communicating to it a greater verisimilitude. 
Pherusa tubulosa, Lamour. Corall. 53, pi. 2, fig, 1. Blainv. 
Actinolog. 453, pi. 80, fig. 1.- — Flustra tubulosa, Ellis and Soland , 
