11 



it has the form of a wide and deep canal leading forwards from the branchial 

 cavity (fig. 2. pi. 3.). This overlapping takes place along the inferior or ventral 

 side of the tube ; and the right margin lies over the left. Within the funnel, but 

 on the opposite side and near the external orifice, there is situated a flat, fleshy, 

 tongue-shaped process (e. fig. 2. pi. 3.), rounded and thin at the extremity, which 

 is directed towards the external orifice of the tube. The length of the unat- 

 tached part of this process is ten hues, its breadth at the base seven lines. The 

 parietes of the tube which are covered by this process, are extremely thin, and 

 almost membranous. 



The description of the funnel in Rumphius has been considered very obscure, 

 if not incomprehensible* ; but with respect to the latter part, or tongue-shaped 

 valve {een tonge), a structure precisely analogous, though less developed, ob- 

 tains in Sepia and Loligo. Its probable use is to act as a valve to the orifice of 

 the vent-tube, and prevent the ingress of water or other substances when the 

 animal moves forward, or is retained at anchor with the head against a current ; 

 and it seems to confirm this view of its use, that in Octopus, which possesses 

 neither elongated pedunculated arms nor lateral fins for propelling itself for- 

 wards, the infundibulum is unprovided with such an appendage. 



The sides or crura of the funnel (/. g. fig. 2. pi. 3 ; h. pi. 5.) diverge, 

 and pass upwards and backwards along the outer part of the muscles of ad- 

 hesion ; they form the smooth surface uncovered by the mantle behind the head, 

 which is seen at m. pi. 1 , and are separated from the head by a constriction or 

 neck. 



The head of Nautilus is of a conical form, and of a much denser texture than 

 the analogous part in the Dibranchiate Cephalopods : it is excavated in such a 

 manner as to form a receptacle or sheath, into which the mouth and its more 

 immediate appendages can be wholly retracted, when they are so completely 

 concealed as to require the aid of dissection before they can be submitted to 

 examination. 



The orifice of this great sheath (which from its protecting all the parts con- 

 nected with the mouth I have termed oral) is anterior ; its superior parietes are 

 formed by a thick triangular plate or hood («. pi. 1 ; h. pi. 2; fig. 1. pi. 3.), 

 with a wrinkled and papillose exterior ; the sides give off" numerous conical and 



* See Diet, des Sciences Nat. xxxiv. p. 291. 



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