90 Dr. A. Philippi’s Zoological Notices. 
ventral margin, but with the anterior margin ; so that the point 
of commencement of the shell is situated at its hinder end, 
and not at the vertex (Wirbeln), as in other Conchylia. It 
appears that a great portion of the dorsal margin is subse- 
quently re-absorbed. The vertices thence appear in part un- 
cinate. The left adhering shell is exceedingly thin, other- 
wise similar to the other. The two shells inwardly, as well 
as the tube, are of a nacreous lustre; thus rendering it 
extremely difficult to distinguish mantle and muscular im- 
pressions. A hinge is entirely wanting, and there is even no 
peculiar cartilaginous ligament ; I merely find a weak fibrous 
corneous ligament. (Fig. 4 4.) Where the two shells touch 
one another at the back there is frequently a projection in the 
tube, and we in general meet with an oblique projection 
(Vorsprung) where the space for the shell ceases and the true 
tube commences. The spinoid tubes are present; they are ir- 
regular, and are only employed by the animal where it finds 
a free space in the Balanus mass. They are in general lost 
on loosening the house, so that rarely any other trace remains 
of them than the point-like apertures in the interior of the 
shell, as I have represented in fig. 2 e. In some successful 
cases, however, they are seen very distinctly. 
The animal has exactly the form of a sack, which in front 
has but avery small fissure, out of which the apex of the very 
thin foot can scarcely exsert itself. (Fig. 1. and 4.) Poste- 
riorly the mantle is prolonged into two siphons, cohering nearly 
to the apex, which reach to the extremity of the tube. The 
common portion of the siphons terminates with a fringed 
border, and then follow two very short tubes, of which the 
inferior or branchial siphon is broadest. Both are provided 
at their aperture with simple cirrhi, and are carmine red, 
while the remainder of the animal is colourless. It has, 
moreover, to be observed, that the common tube before its 
border is covered with a quantity of grains of sand, which 
are not easily separable from it. (See Fig. 3.) Fig. 4. ex- 
‘hibits the animal, after having been some time in spirits, 
lying on the right shell. The two adductores, of which the 
posterior one is round and large, the anterior one kidney- 
shaped and small, are at present very distinct. If the mantle 
is cut open in the ventral line, it is first observed that the 
mantle -in the ventral side is very thick and fleshy ; poste- 
riorly the strong muscles which draw back the siphons are in 
view ; in the centre, the semicircular branchiz, out of which 
the small narrow vermiform foot (d in fig. 5. and 6.) projects ; 
and above this, on each side, two very long, linear, somewhat 
curved appendices buccales,c. On each side there is only one 
