1895 - 96 .] Mr Arthur T. Masterman on Phoronis. 
61 
jects over the branchial space at an angle, and evidently serves to 
sheer off the water current and direct it through the branchial 
fissure into the atrial space. 
The epistome is continued as a ridge projecting across the floor 
of the branchial chamber the whole way round the coils, which 
ascend in a spiral, so that it forms a beautifully constructed appara- 
tus for separating the water and food currents. 
The third type is the atrial epithelium, the cells of which are 
small, compact, and cubical, with large nuclei ; they usually have 
numerous pigment spots, and are mostly non-ciliated. This type 
lines the whole atrial space except the lophophoral organs and the 
nerve ring, and the branchial fissure, so that the upper surface of 
the epistome is (in the median line) covered with this epithelium, 
the lower surface with the branchial type. 
Nervous System . — This is ectodermal, and has been described by 
Diagram of Longitudinal Section through Phoronis to one 
side of median line. 
various workers, Avho do not, however, agree entirely. Cori gives a 
detailed account of the nerves in P. psammophila, with which I find, 
« — — - 
Diagram of Longitudinal Section through Phoronis through median line. 
In each diagram the branchial epithelium is thick-, the atrial thin- lined. 
for the most part, P. australis agrees, except that, as Benham stated, 
there are two longitudinal nerves (paired) near the lateral mesentery. 
