36 



Charles Zeleny. 



In Pomatoceros triquetroides 21 specimens were examined and 

 all had the operculum on the left side. This makes a fairly 

 strong probability in favor of the permanence of such a charac- 

 teristic. As a further argument may be mentioned the statement 

 of de St. Joseph ('94), who mentions the observation of Grube on 

 63 specimens of P. triqueter, L.( = P. triquetroides, D. Ch.) and of 

 himself on many more than this number which showed the oper- 

 culum in every case on the leftside, so that we maybe fairly certain 

 that in this species the organ is a permanent structure of the left side. 



In Vermilia multivaricosa eleven specimens were examined. 

 Six had the operculum on the right and fve on the left side. In 

 this case, therefore, there seems to be a fairly equal distribution 

 between the two sides. 



The data for Group VI are collected in the following table :^ 



Table VII. Group Six. Position of Operculum. Locality: Bay of Naples. 



Name and Date. 



No. Operc. 

 Right. 



Operc. 

 Left. 



Per cent Per cent 

 Right. Left. 



Ditrupa subulata 



1903/I/10. 

 Spirorbis Pagenstecheri 



1 903/1 to V. 

 Pileolaria sp. (?) 



1903/III/2. 

 Pomatoceros triquetroides 22 



i903/I/25,IV/3,IV/5. 

 Vermilia multivaricosa 



1903/1/16,111/5. 



II 



100 



22 



55 



45 



Discussion of the Evidence from Group VI. In Spirorbis 

 Pagenstecheri and Pileolaria sp. the position of the operculum 



^Former obserrations on the position of the operculum in this group are those of Caullery and Mesnil 

 ('96), who state that dextrally coiled Spirorbis-like Serpulids always have the operculum on the right 

 side (example — Spirorbis Pagenstecheri) while sinistrally coiled ones have it on the left side (example — 

 Pileolaria sp. [.']). de St. Joseph C98) describes the operculum of Ditrupa subulata, Desh., as a struc- 

 ture of the left side, de St. Joseph ('94) for himself and also for Grube describes Pomatoceros trique- 

 troides as always left-handed. 



