710 PROTOCOXCHS OF CERTAIN PORT JACKSON GASTEROPODA, 



suggest that it may be that where no varix has been thrown up 

 the mollusc has left no conchological record of the nepionic period. 



The arguments which might be advanced in support of this 

 suggestion are of necessity only deductive and analogous, and 

 therefore not conclusive; but they are sufficiently so to defend 

 my use of Hyatt's term ananeanic (Hyatt, Zool. Anz. No. 427, 

 1893, p. 327) for early adult structure instead of the term brephic 

 ( = nej)ionic) used by Harris {loc. cit.). 



It will be noticed that the descriptions are of " Protoconchs " 

 and "Apices." The distinction is perhaps arbitrary, but never- 

 theless useful. The former term is applied to a detached embryo, 

 the latter to one which is attached to some adult structure."^ 



Before proceeding to describe the apices, it may be deemed 

 fitting to give an account of my mode of identifying them. 

 Whilst sorting sand, shells are met with which are at once 

 recognisable as young; these are the material on which I start to 

 work. In some instances specimens consisting of a protoconch 

 and only one adult whorl are identifiable, but in most cases a 

 series illustrating the growth up to the paraneanic and even the 

 ephebic stages, is needed before the young can be identified with 

 certainty. Murex anstralis, Quoy &: Gaim., is illustrative of the 

 former instance, whilst Tritonium fusiforme^ Kiener, is illus- 

 trative of the latter. I had to obtain an almost complete set of 

 specimens, that is, a series illustrating almost every stage in the 

 growth of the shell, before I could determine its young satisfac- 

 torily, I have found it more practical to obtain the young shells 

 first and refer them to adults, than to take an adult shell and 

 determine to find its young. I would warn students from iden- 

 tifying young shells hastily; some of them are very deceptive; 

 for example, the sculpture and general appearance of T.fusiforme 

 up to the end of the paraneanic stage are so suggestive of T. 

 exaratiis. Reeve, that I at once put it down as the young of that 

 species, and it was only when I had obtained a large series of 



* For the purposes of this paper I have found it convenient to speak of all 

 post-embryonic structure as adult structure. 



