BY H. LBIGHTON KESTEVEN. 327 



nomenclature would result. In fact, such a proceeding would be 

 an unwarranted piece of pedantry; some such term is necessary, 

 therefore that which already has a currency should be used, and 

 at its current value. Grabau(l) has suggested that " protorte- 

 conch " would be more explicit than the term under considera- 

 tion; in comparing the bulbous protoconch with the twisted pro- 

 torteconch, the term will doubtless prove useful, but except in such 

 cases its use is rather to be deprecated; it is in this way, 

 apparently, that its author would use it. 



ii. — The Ontogenetic Stages. 



The names which I would give to the four component parts of 

 the ideal protoconch are — Phyloconch, Veloconch, Nepioconch and 

 Ananeanoconch, and their definitions as follow : — 



1. Phyloconch. — This is the " primitive" shell of Lankester.(6) 

 It is formed by almost every member of the phylum, but, with 

 rare exceptions, it is shed at an early age and does not enter into 

 the composition of the protoconch. 



2. Veloco7ich. — The greater portion of this is formed during 

 the veliger stage, though it may have been begun just before that 

 stage. 



3. N'epioconch. — This is formed during thenepionic stage, but, 

 for reasons given in a preceding paper, (4) I am inclined to regard 

 it as of rare occurrence. 



4. Ananeayioconch. — Formed during early neanic stages. 



The phyloconch is, as already stated, the "primitive shell" of 

 Lankester, and has been noted in every Gastropod of which the 

 development has been studied. Sometimes it takes the form of 

 a chitinous plug filling the first shell-gland. The phyloconch is 

 very generally shed, but when retained it may be detected in the 

 very young protoconch; instances of this are Clausilia, Nerithia, 

 and Paludiyia. In these, however, it is so minute that, had not 

 the development of the molluscs been studied, it is doubtful 

 whether its presence in the protoconch would have been detected; 

 in view of this fact, it appears likely that only by the method 



