184. H. LEIGHTON KESTEVEN. 
termed respectively: Phyloconch, Veloconch, Nepio- 
conch, and Neanoconch. 
Before proceeding to define these conchogenetic stages it 
may be well to explain why I retain, and use in these defini- 
tions, the term ‘‘ protoconch.” 
The ‘ protoconch,” in the accepted and almost universal 
interpretation of the term, consists of an indefinite number 
of the apical whorls of a Gastropod shell, irrespective of 
whether these apical whorls are the first shell or not. Dall (1) 
speaks of the Scaphella protoconch, well knowing that the 
structure so designated was formed subsequent to a horny 
bulb-like shell, which was discarded in the egg capsule. I 
have, myself, described the “ protoconchs” of numerous 
species of Lotorium (No. 4), being at the time well aware 
that what I described were but calcareous casts of the horny 
veliger shells. Since, then, the term has attained to a general 
acceptance, to change its significance would immediately cause 
confusion ; to attempt to discard it altogether would have the 
same effect. I say “attempt” advisedly, for it is not to be 
supposed that such a suggestion would receive immediate 
and universal approbation. Moreover the term is a useful 
one; it is here used in the above broad sense, namely, to in- 
clude those apical whorls, disregarding their age, which by 
smoothness, distinctiveness, or size are differentiated from the 
succeeding whorls, and thereby indicate that at their con- 
clusion the mollusc entered upon a new and important onto- 
genetic phase—such, for example, as the change from veliger 
to sedentary life, or the emergence from the egg capsule. 
B. A ConcHOGENETIC NOMENCLATURE. 
Phyloconch.—The name is taken from the fact that 
it is formed by the first distinctive “ Phylum” character 
to appear. Itis the “primitive shell” of Lankester, and is 
formed by almost every member of the Phylum, but, with rare 
exceptions, is shed at an early stage, and does not enter into 
the composition of the protoconch. 
Among Prosobranchs it is retained by Neritina. 
