Microscopical Society of Victoria. 
23 
the RacMglossa. He includes the genera Navicella , Nerita 
and Neritina in his family of Rhipidoglossa . 
Without entering into the niceties of these distinctions 
it will he seen that the radula is now recognised as 
occupying an important position in molluscan economy, 
and that Australian observers can largely contribute to the 
conclusions which await facts to determine them in one 
way or another. It is certain that our coasts possess a 
laro-e number of important and characteristic forms, the 
dentition of which are quite unknown. And even amongst 
our land and freshwater shells important results may be 
expected. The very fact of an animal belonging to a 
well-known genus does not necessarily imply that its 
dentition will not depart from the normal type. Messrs. 
Bland and Binney, in America, have revised much of the 
classificatian of the land shells by a study of the radula. 
See especially their remarks on Shuttleworth’s genus 
Gceotis, in the 10th vol. of the “ Annals of the Lyceum of 
Nat. Hist, of New York.” The same authors describe and 
figure the jaws and radula of a Physa , with a finely striated 
shell from Guadeloup, which departs widely from the 
generic type. The radula is quite different, and presents 
none of those long transverse ranges of teeth in the form 
of a comb which is characteristic of the genus. Mr. Binney, 
a^ain, in the “ Proc. Academy of Natural Sciences of 
Philadelphia, U.S.,” vol. 2, part 3, p. 140, gives most 
interesting and important details on the jaws and radula of 
the terrestrial pulmoniferous mollusca of North America. 
I These observations are the results of Mr. Binneys labours 
during the last thirty years. He deals with the best 
methods to extract the jaw and radula, and gives the most 
ample details of their position and the modus operandi, so as 
not to injure the delicate membranes. Mr. Binney thinks 
that the jaw and radula furnish together a good basis for 
classification, and from the results of an examination of 
a very large number of species he divides the whole of 
the known terrestrial pulmonata into two great divisions, 
characterised by the absence or presence of a jaw. Those 
destitute of that organ are also deficient of lateral teeth ; 
some being without centrals, but all having aculeate 
marginal teeth. The genera Onchidiuui } Onchidella, 
Peronia, and perhaps Buclianania are characterised by 
their quadrate marginal teeth. For the second division. 
