new Species of the Genus Solenopus. 
325 
contract, and forms the proper entrance to the branchial 
cavity. This is ovate from behind forwards, 6 millims. in 
length and 4 millims. broad in the middle. The branchiae 
are arranged in the form of an oblong circlet, consisting of 
thirty filiform tubules, of which those nearest the back are the 
longest, and those towards the ventral surface are extremely 
short. At the bottom of the branchial cavity is the round 
anal orifice. Above and behind the branchial cavity, exactly 
upon its margin towards the dorsal surface, there is a thick 
round papilla, in the middle of which is a fine aperture for the 
generative organs. 
The skin or mantle, which is thick and firm, is beset all 
over with numerous calcareous spicules, which give it a shi¬ 
ning appearance. These calcareous spicules are of four diffe¬ 
rent forms : on the dorsal keel they are alternately spear- 
shaped, lancet-shaped, and needle-like; on the rest of the 
mantle they are lancet- and needle-shaped. The skin is 
covered with a single layer of cylindrical epithelial cells, in 
the midst of which there are, at tolerably regular distances 
apart, large round cells, which project above the level of the 
rest of the epithelium, and are filled with a granular mass. 
These are probably unicellular mucus-glands, and are most 
likely the bodies described by Tullberg as warts in the skin. 
Beneath the epithelium the mantle consists of a homogeneous 
tissue, in which a fine striation may be detected here and 
there. Imbedded in it are vessels, muscles, and nerves. The 
vessels are tolerably numerous, partly empty, partly filled 
with detached oblong cells; in many places they run into 
pointed canals, terminating ctecally, which are completely 
filled with a granular protoplasm. The muscles run partly 
in bundles, partly as single fibres in all directions; only to¬ 
wards the inner surface are they somewhat regularly arranged 
in longitudinal and annular positions. 
Alimentary Organs. 
The buccal mass is thick and muscular, and has anteriorly 
a round aperture without teeth, from which start two long 
cushions, which project down into the oesophagus; the latter 
is tolerably wide in the middle, but where it passes into the 
stomach it is narrowed and surrounded by a sphincter. The 
stomach occupies nearly the whole of the body-cavity; its 
walls are firmly affixed to the mantle, except above, along the 
back, where the genital gland is placed between the mantle 
and the stomach. Its inner surface is strongly folded. The 
folds are broadest in the middle, between the dorsal and 
