TIE INTELLECTUAL OBSERVER. 



MARCH, 1864. 



THE DENTITION OF BEITISH MOLLUSCA. 



BY THE EEV. G. KOWE, M.A. 

 (With a Tinted Plate.) 



By way of preface, it will be well to remind the reader that 

 the class Mollusca admits of a general subdivision into Acepha- 

 lous and Encephalous animals, the latter alone possessing heads. 

 And although it by no means follows that they should therefore 

 possess teeth, or that their headless relations should not have 

 these useful instruments, yet it is among the JEncephala, or 

 Gasteropods, that we find the subjects of our present observa- 

 tions. These creatures are also, for the most part, occupants 

 of a single shell, such as that of the whelk and the limpet, but 

 some, as the land-snails and the beautiful nudibranchs of the 

 ocean, are naked. 



The teeth of a Gasteropod do not answer to the ordinary 

 signification of the term. They are organs of trituration and 

 abrasion indeed, but are not used for the purposes of holding 

 or biting. Many of the shell-less mollusks have one or more 

 horny mandibles ; and in some instances these are replaced, and 

 even supplemented, by buccal plates armed with spines. Such 

 is the case with the genus Natica, and with Cyprcea Europcea. 

 And Woodward states, that many of the flesh-eaters have a spiny 

 collar at the end of their flexible proboscis. These afford the 

 means of holding the food or prey, while, what I have here 

 termed teeth, are employed in rasping it into the mouth. The 

 so-called teeth are silicious plates of extreme tenuity, often 

 beautifully outlined and curved, and frequently serrated at their 

 edges. There are generally a great number of them, some- 

 times many thousands, in one animal; and they are rooted in a 

 thin membrane, named, from its form and position, the dental 

 or lingual ribbon. As this lingual band forms a very in- 

 teresting object for the microscope, and only requires a little 

 vol. v. — NO. II. G 



