Two new Opistobranchiathe Mollusca 

 from the Red Sea. 



Accompanied by a list of references to the genera Notarchus 

 Cuvier and Hexabranchus Ehrenberg 



by 



Richard Hagg 



of Upsala. 

 With a plate. 



*■ 



The following two species, hitherto unknown to scholars, 

 were collected at Tor, situated on the Eed Sea, by the Swedish 

 Zoological Expedition in the month of June 1901. 



Notarchus brevipes n. sp. 



(Figs. 1 — 3 natural size.) 



Length 114 millims, greatest breadth (on the middle) 45 

 millims, greatest height (at the opening of the branchial cavity) 

 31 millims. Head not distinguishable from the main body. Mouth 

 longitudinal with plicated lips; it is situated on the middle of the 

 underside of the head. The anterior tentacles are fixed to the 

 side of the mouth. They are laminate, without any lobes or pro- 

 cesses, only supplied with three small thready appendages at the 

 exterior part of the anterior front border. They are attached to 

 the head with the median and inner portion of the anterior 

 border. The posterior border is convex outwards. Their length 

 is 7 millims. The posterior tentacles (rhinophores) are fixed to 

 the upper side of the hind part of the head. They are tubular. 

 Their edges are not, however, grown together. At the ends 

 they are open. They are supplied with several thready appen- 



Jayershiold : Expedition. 0. (6J 1 



