INTRODUCTION. 



The Tertiary MoUusca of Australasia present many features of 

 special interest, both to geologists and zoologists. The remarkable 

 abundance and perfect state of preservation of the Gastekopoda, 

 especially of Victoria, enable us to shed much light on certain 

 questions relating to phylogeny, which cannot fail to assist the 

 zoologist as indicating the oiigin of many of the principal groups 

 of that division of the Mollusca, and as imparting some idea 

 of the past history of the modern molluscan fauna of Australasia 

 generally. The larval shells, especially, have proved to be 

 of great interest, and I venture to think that many of the 

 details concerning them as recorded in this Catalogue will prove 

 serviceable, not only from the phylogenetic standpoint, and in 

 regard to the early history of the individual, but as a contributii)u 

 to the systematic classification of the Gasteropoda. The phenomena 

 of growth in this division of the mollusca have never been studied, 

 except in regard to restricted groups; and I have occasionally 

 criticized modern methods that give undue importance (as it would 

 seem) to the number and disposition of plications on the columella, 

 the absence or presence of liriE within the outer margin of the 

 aperture, the relative length of the anterior canal when present, 

 and modifications in detail of external sculpture. These and 

 kindred phenomena aie frequently utilized by the systematist for 

 purposes of specific and even of generic classification, whereas 

 in many instances a careful study of ontogeny would show that 

 they were mere peculiarities either of the individual or as 

 characterizing a distinct stage of growth. I do not intend 

 to imply that the features of growth just mentioned are never 

 of importance for purposes of classification ; but until each case 

 is studied on its own merits, in other words until the ontogeny 

 of each has been carefully worked out, it is impossible to say 



