326 NOTES ON PROSOBRANCHIATA, IV., 



sand have provided me with much useful material. Several 

 genera have been studied as extensively as was Lotorium (3), but 

 as there was no such immediate call for descriptions and figures 

 of their protoconchs as there was in that case, I have not thought 

 it desirable to publish the results. 



When No. iii. of the present series(4) was written, I had been 

 led to the conclusion that in some instances, e.g.^ Cyniatiunij'^ 

 the so-called protoconch was really a secondary shell, and there 

 suggested the term " pseudoprotoconch " for such. A more 

 recent study of the protoconch of Jlegalatractus aruanus Linn. (5) 

 has convinced me that a protoconch may be composed of portions 

 formed during one or all of four important stages of early growth. 

 An ideal protoconch would, in my conception, be composed of — 

 (I) the plug of the primitive shell-gland, (2) a portion formed by 

 the veliger, (3) a portion formed during the nepionic stage, and 

 finally (4) a portion formed during early neanic stages. 1 am 

 therefore now inclined to withdraw the term pseudoprotoconch 

 and replace it with the more explicit terms nepioconch and 

 ananeanoconch proposed below. 



Before proceeding to the purpose of the present paper, namely, 

 a definition of and nomenclature for the above four conchyliaceous 

 developmental records, I would justify my retention of and 

 incidentally define the term "protoconch," which the conclusions 

 herein set forth would seem to show to be a redundant misnomer. 

 The term has been in the past, and is here, used to designate those 

 few apical whorls which differ markedly either in contour or 

 sculpture, or both, from the succeeding structure, which latter I 

 have, for want of a better term, designated "adult structure." 

 In the above sense the term " protoconch " is certainly useful, 

 and even were I to advocate that it be no longer used, and were 

 to coin, or make use of, some more explicit term, I am unable to 

 flatter myself that my advice would be generally followed, a dual 



* The name Cymatium is here used instead of Lotorium (the erstwhile 

 Triton) in deference to the opinion of a growing majority that Bolton's names 

 are admissible as nomenclatural entities. 



