GASTROPOD PROTOCONCH. 187 
phyloconch is a component part of any particular protoconch. 
This method would, of course, be the most satisfactory way 
of ascertaining the presence or absence of any of the other 
portions, but there is also a deductive method which may be 
employed with some degree of certainty. Let me illustrate 
this method with the example which gave rise to this essay, 
Megalatractus aruanus (Linn). 
The large size of the protoconch, as taken from the egg 
capsule, shows at once and conclusively that the veliger 
stage was passed within the capsule. What I have here 
termed the calcareous cast of the veloconch (and in my de- 
scription above referred to “ veliger shell”) is distinctly 
marked off from the neanoconch by a deep encircling groove. 
This groove as certainly indicates a pause between two 
growth-stages as does the varix on the adult shell. The 
most important pause in early growth is the nepionic stage ; 
it is therefore justifiable to conclude that the groove is 
the indication of that stage, and that the preceding structure 
is veliger and the succeeding is neanic. 
If this deductive method is correct, by its use we shall be 
enabled to give a brief outline of the early developmental 
history of any particular testaceous Gastropod. 
In conclusion, I would draw attention to the fact that the 
above nomenclature will very likely prove applicable to the 
Pelecypods equally with the Gastropods. 
Works REFERRED TO. 
Dati, W. H.—‘ Trans. Wagner Free Inst. Sci.,’ iii, pt. 1, 1890. 
. Fiscner, Paut.—‘ Manuel de Conchyliologie,’ p. 679, 1887. 
. Kesteven, H. Letenton.—‘ Proc. Linn. Soc. N.S. Wales, xxvi, pt. 4, 
pp. 709 e¢ seq., 1902. 
. Kesteven, H. Letauton.—Zoe. cit., xxvii, pt. 3, pp. 443 e¢ seg., 1902. 
. Kesteven, H, Leteuton.—Zoc. cit., xxviii, pt. 2, pp. 443 e¢ seg., 1908. 
. Kesteven, H. Lerauton.—‘ Mem. Aust. Mus.,’ v, pt. 8, 1904. 
. Lanxester, E. Ray.—‘“‘ Mollusca,” ‘ Encye. Brit.,’ edit. 9, xvi, 1885. 
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