6 
D. C. Danielssen. 
[No. i. 
apart from each other, and which do not form pairs; neither is 
there anything that serves to indicate that any of them take the 
place of directive septa as is usually the case in the Actinidæ; 
but they extend themselves from the posterior part to the oral 
dise, and secure themselves to the intestine and the gullet-tube 
(Oesophagus) in the whole of their length (Pl. I fig. 7, 1 1 a) causing 
the body-cavity to be divided into 12 chambers (Pl. I fig. 7 b), 
which at the top, round the gullet-tube, are rather broad but ex- 
tremely narrow round the rectum. 
These septa are usually furnished with transversal and longi- 
tudinal muscles but, still, the arrangement is somewhat different 
from the usual one. The transversal muscles appear to be little 
developed, and are almost entirely covered by the longitudinal 
muscles that occupy both surfaces of the septa. At the origin of 
the septum in the wall of the body, the longitudinal muscles divide 
themselves in such a manner, that one portion extends along the 
inner surface of the wall of the body, and form the 12 strong lon- 
gitudinal muscles which are attached by loose connective-tissue to 
it (Pl. I fig. 2 a, 5 a, 7 c), and that may even be recognised in 
the 12 longitudinal areas on the exterior surface of the body; ano- 
ther portion distribute themselves over both surfaces of the septum 
(Pl. I fig. 7 d), and follow these to the gullet-tube (Osophagus) and 
intestine. From the connective-tissue of the septum (the sup- 
porting membrane) proiongations issue, which become ramified, and 
the muscle-fibres are secured to these, causing the longitudinal 
muscles to acquire a fruticous appearance, which indeed is rather 
common among the Actinidæ. 
They are most fully developed at the origin, and in proxi- 
mity to the oesophagus and intestinal canal; in the middle they 
are much thinner, and there the connective-tissue membrane appears 
altogether to be thinner (Pl. I fig. 7). But besides the 12 longi- 
tudinal muscles that follow the inner wall of the body, there is, 
besides, upon it, a layer of strongly developed transversal muscles 
that collect together into regular ribbons, placed at uniform di- 
stances apart (Pl. I fig. 5 b) and which pass under the longitudinal mus- 
cles to the septum (Pl. I fig. 5 c). They lie, therefore, in each 
chamber, and impart to the inner surface of the integument, both 
by their regularity and their transsection by the longitudinal mus- 
cles, a trellised appearance (Pl. I fig. 5). The musculous layer is 
everywhere, both on the septa and the wall of the body, clad with 
an endothelium, consisting of long, ciliating, cylinder cells, but how 
