24 
Quarterly Journal. 
those possessing jaws, the genera are arranged into two 
families, namely, those with quadrangular, and those with 
aculeate marginal teeth. The following genera possess 
teeth of the aculeate type: Limax , Ibycus, Parmacella, 
Tementia , Marietta, Parmarion , Dendrolimiax, Vitrina, 
Vitrinoidea , Vitrinopais, Nanina , Stenopus , 
Mdcracyclis , and Zonites. The remaining genera have 
quadrate marginal teeth, and are divided into three sections, 
according to the character of the jaw, which is either in 
one single piece, or one single piece with an accessory 
upper quadrate piece, or in numerous pieces. Then follows 
an essay on the value of the jaw and radula for the purpose 
of classification. 
My own observations are epitomised in the essay on the 
molluscan fauna of Tasmania.* I may say that a fact 
which I have not seen prominently brought forward by 
any of these writers is that the radula is often a tube. 
The term ribbon is therefore unfortunate, as the organ is 
by no means a strap-shaped membrane with teeth set 
upon it. The basal membrane is in most cases the only 
part preserved, the upper and enclosing portion which 
goes over the teeth is of such extreme tenuity that it 
is destroyed in drying. This I believe to be the structure 
when the teeth are few in number, as in Patella and 
Littorina. In Siphonaria the membrane is broad and 
strap-shaped, and in dentition it approaches the pulmoni- 
ferous freshwater mollusca, of which it is the marine 
representative. When the animal is alive the radula is 
a tube, a small portion of the lower and outer edge being 
everted for the purpose of feeding. In all our LiitoHnida ?, 
which includes, in my opinion, properly speaking, very few 
genera—as I should suppress jRieella and Tectavia —the 
radula is a long narrow transparent tube, with three 
cuspidate teeth on each side of a small central one. The 
membrane and teeth are quite colourless, and lie coiled 
up in the stomach, or perhaps just above the stomach, at 
the back of the head. My opinion is that all the food has 
to pass along the whole length of this tube before reaching 
the stomach, and it is then in a sufficiently fine state of 
subdivision for assimilation. In the PatellidCB we have a 
very long radula, the teeth being a deep brown colour, and 
* See Proc. Eoy. Soc. N.S.Wales, 1878. 
