PTEAMIDELLID^:. 401 



termination to an antepenultimate one. I apprehend that 

 these minute lobular appearances are due to the retractors of 

 the tentacula concentrating at their tips a portion of the 

 flake-white markings that are seen on those organs in all the 

 Chemnitziee, and have no functional attribute beyond what is 

 common to all tentacula. 



I have to add, in respect to the proboscis of Chemnitzia, 

 that the organ is long, flattish, at least so in appearance, 

 broad at the base, gradually tapering to its minute orifice; 

 the terminal half in the Ch. plicata example is tinged with 

 dull sulphur-yellow, like that of the body, neck, and rostrum . 

 After the proboscis was fully protruded, in about a second, 

 I saw, through the hyaline texture, another organ unroll 

 itself from base to point, from which one would infer, that 

 the inner cylinder, if it be one, is not fixed to the inside 

 terminus of the outer tube ; or it is possible that the organ 

 I saw ascend from the base of the proboscis, might be the 

 very long, flat, unarmed lingual riband. 



With regard to what I term the rostrum, M. Loven says, 

 " that the mentum has been misunderstood, and has generally 

 been supposed to answer to the muzzle of Turbo, but that is 

 not the case; this perfectly formed part is what I would call 

 the mentum, the muscular mass, which is so extremely deve- 

 loped in Natica, covering part of the tentacula and mouth." 

 With respect to this extract, I cannot concur. The mentum, 

 which I call the rostrum in Chemnitzia, has very little ana- 

 logy with the upper part of the foot in Natica, which I admit 

 is always spread on the anterior part of the shell, as M. Loven 

 observes ; but then I cannot call the anterior portion of the 

 foot a mentum. What M. Loven calls the mentuin in Chem- 

 nitzia, is never spread on the upper part of the shell, and does 

 not in any case touch it, and has no more connection with the 

 foot than the muzzle of Rissoa ; both are tied to the foot of 

 their respective genera by a pedicle or bridle., which junction 

 happens to be more anterior in Chemnitzia than in Rissoa, on 

 which point see Ch. elegantissima and Ch. pusilla. 



I must here remark, that the labium, which exists more or 

 less conspicuously in every Gasteropod, is particularly deve- 



2 D 



