Notarchus and Hexabranchus. 5 



thoroughly unbranched, processes. Such are completely wanting 

 in the species in question. The two large, fingerlike processes 

 (one on each side) in front of those referred to are likewise 

 thoroughly wanting. 12) The rather large black annular spots 

 with the light point in the middle, which are to be found on 

 the upper side of the back part of the body of N. savignanus, 

 are lacking. 13) The foot is spotty. 



That the gill is largely situated outside the branchial cavity 

 in the species here described, but in N. savignanus is represented 

 as situated inside the same, is certainly no mark of distinction. 

 For Sanders-Rang (in Histoire naturelle des Aplysiens) states 

 that the gill of a related species is usually kept outside the 

 branchial cavity when the animal is moving, but that it is other- 

 wise kept inside the same 1 . 



Hexabranchus plicatus n. sp. 



(Figs. 4 — 5 natural size.) 



Length 100 millims, greatest breadth 95 millims. height 22,5 

 millims. Body nearly circular, glabrous. If the mantle is not 

 taken into account, it is elliptic. The dorsal surface is vaulted 

 and divided from the border by means of a depression. The 

 mantle is expanded round the whole of the body. It gradually 

 passes into a thin border. The greatest breadth of the border 

 in front of the head is 23 millims, on the middle 23 millims, 

 behind the anus 16 millims. On the edge it is considerably 

 plicated, with the exception of the front part of the head, where 

 the plicature is insignificant. Mouth on the front part, subjacent. 

 On its sides the fleshy, flat, kidney-shaped oral tentacles are 

 situated. Each tentacle bears 8 large lobes. The lobes are club- 

 shaped at the end. Each lobe has a shallow indentation on the 

 middle. The length of the tentacles is 9,5 millims, their greatest 

 breadth 8 millims. On the upper side of the body, close to the 

 front end, there are two rhinophores. Their exterior part is lami- 

 nated and. bent back. It gradually narrows towards the point. 



1 Since writing the above, I have been informed, that the fact that the 

 gill of the specimen here described is situated outside the branchial cavity. \a 

 probably due to its having been narcotised with fcobaOCO. 



