4 
D. C. Danielssen. 
[No. i. 
to the nature of the contractions (Pl. I fig. i). The exterior sur- 
face of the body is smooth and shining, and it has 12 longitudinal 
furrows, between which the same number of broad longitudinal 
areas are seen, extending, like the furrows, from the posterior oral 
disc to the outermost extremity of the animal (Pl. I fig. 1); and 
furnished with a multitude of extremely small suckers, only to be 
observed with the aid of a powerful magnifying glass, and which 
do not appear to be placed in any systematic arrangement (Pl. I 
fig. 14). On the anterior part of the body, on the contrary, the 
suckers are somewhat larger and appear to arrange themselves 
in series. 
When the tentacles are extended, the anterior third part of 
the body is somewhat tumified, and the integument becomes, then, 
so far transparent that septa, which show themselves to correspond 
to the longitudinal furrows that indicate their insertions, may be 
distinguished. The medial part of the body is not quite so much 
expanded, and not quite so transparent; but the posterior part, 
which composes about a fourth part of the whole length of the 
body, is narrower, perfectly opaque, and incapable of being re- 
tracted, although it still becomes expanded occasionally, and its 
integument then becomes partially transparent; whilst the medial 
part contracts, at same time becomes narrower and almost per- 
fectly opaque. Altogether, the body alters its form very consider- 
ably, according as the animal expands or contracts itself. 
At the extremity of the posterior part a minute round aper- 
ture is seen (Pl. I fig. 4 a) surrounded by 12 extremely small 
folds or papillæ (Pl. I fig. 4b). When the aperture dilates itself it 
is always stelliform, and there is, in that state, frequently ejected 
sand or excrementa, after which it is very firmly closed, so that 
there, then, is only a stelliform depression visible. 
The oral disc is conically protuberant (Pl. I fig. 1), and fur- 
nished with 12 rather broad folds that collect round the oral 
aperture (Pl. I fig. 12) which is rather round, with smooth but 
thick lips, and no gonidia. The margin of the disc is round, and 
upon it there is seated a cycle of 12 tentacles occupying a space 
equal to about one third of the length of the body (Pl. I fig. 1 and 12). 
The tentacles are retractile, cylindrical, and tolerably slender, and 
terminate almost filamentously. Not only the tentacles, but also 
the oral dise may be retracted and quite concealed by the superior 
margin of the body. 
