12 
D. C. Danielssen. 
[No. i. 
body are arranged in series. The integument, when the animal is 
in full vigour and has its tentacles extended, transparent; so much 
so that the septa with the mesenterial filaments may be distin- 
guished. The oral dise conically protuberant, has an almost round 
oral aperture from which 12 folds issue towards the periphery. 
No gonidia. 12 tentacles, having about a third part of the length 
of the body, retractile, attenuated, terminating almost filamentously. 
The uppermost margin of the body may be drawn over the oral 
disc. During the contractions the integument acquires a chequered 
form. The Colour. The anterior part of the body is almost 
pellucid, with a reddish play of colour; the medial part is flesh- 
coloured, with lighter coloured longitudinal stripes; the posterior 
part has, when it is extended, about the same colour as the an- 
terior part, but when contracted is also flesh-coloured. The oral 
disc is almost pellucid, with faint rosy-red rays having a violet play 
of colour. The tentacles light-red, almost pellucid; at their base 
a brown violet patch prolonging itself as a stripe along the adoral 
side right up to the point. 
Genus-Ægir. 
The body elongate, cylindrical, with a mucous vaginal covering 
and 12 longitudinal ribs between which small suckers are scattered. 
One cycle consisting of a few tentacles. In the posterior part of 
the intestinal canal (Rectum), immediately above the anus, 12 slender 
fissures communicating directly with the intestinal passage. 12 
equally situated perfect septa. Endodermal circular muscles. Her- 
maphrodite. 
Ælgir Mgidus. 
pi. 11 % i, 5— 11. 
The body cylindrical, about 30 m. m. in length; 8 — 10 m. m. 
in breadth in the anterior extremity, and 4 — 5 m - m - m breadth in 
the posterior, somewhat rounded, extremity (Pl. II fig. 1). The 
external surface of the body has an extremely thin, mucous, slightly 
encrusted covering, and is furnished with 12 rather protuberant ribs 
(Pl. II fig. 5 a) between which slightly depressed longitudinal areas 
