6 Richard Hagg. 



The length of this part is 7 millims. The rhinophores are 

 placed in a sheath, the exterior part of which — as far as it 

 is distinguishable from the body — has the length of 2,5 millims. 

 Its edge is entire. 



The length of the foot is 83 millims, its breadth 14 millims. 

 It is nearly all over of the same breadth, only a trifle narrower 

 at the hind end. The front and back ends are rounded. The 

 edge is strongly plicated in the dead animal; this was not, 

 however, always the case when the animal was alive. It then 

 showed no plicature at all when creeping. No excavation is to 

 be found on the underside of the front part. Backwards the 

 foot nearly reaches the exterior, free edge of the border. The 

 part of the foot which is placed under the border is free. This 

 part of the foot has the length of 11,5 millims. 



The genital orifice is situated on the front part of the 

 underside, on the right side of the foot, nearer to the centre 

 than to the edge. The anus is to be found on the hind part 

 of the body, in the middle of the dorsal side. Its orifice is 

 somewhat swollen. A little to the right and in front of the anal 

 orifice, the excretory organ opens into an obliquely placed, rimose 

 narrow aperture. On the left, behind the anus, there is a small 

 papilla, the function of which is unascertained. Round the anus 

 there are six strongly developed gills. They are situated at 

 about the same distance from each other. Anteriorly and on 

 the left side of the anus, there is a larger space left between 

 them. Each gill consists of a very thick head stem. This is 

 divided into three short stems, which are very richly ramified. 



According to what has been stated to me, the colour of 

 the living animal was a coralline red, the border was white and 

 the gills were whitish. 



Hdb. Tor on the Red Sea at the exterior border of the 

 coral-reef. 



H. plicatus belongs to a group of species, for which H. prae- 

 textus Ehrenb. (from the Red Sea) may be considered typical. 

 The group comprises, besides this species, also H. sanguineus 

 Rtipp. and Leuck. (from the Red Sea), H. suezensis Abraham 

 (from the Red Sea), H. mauritiensis Abraham (from Mauritius 

 and Rodriquez), H. orbicularis Abraham (from Mauritius), H. 



