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ly ; a short denticle occurs between the fifth and sixth 

 folds posteriorly. 



Diam. maj. 14, miu. 12 mm., ait. 7 mm. 



Hab. : Quang Huyen, Tonkin. 



Type iu the collection of the School of Mines, Paris. 



In its pariétal armature the présent species difïers from 

 P. suprafilaris in the absence of the anterior vertical 

 plate and iu the lower horizontal fold of that species being 

 hère reduced to an elongated denticle. In its palatal arm- 

 ature it difïers in the absence of the vertical ridge uniting 

 four of the folds, and notahly in the présence of the access- 

 ory posterior ridges of the third and fourth folds, that of 

 the third fold being the longer of the two and curving 

 round the posterior notched extremity. This feature I hâve 

 not observed in any other species. The barriers are aiso 

 situate nearer the aperture than in P. suprafilaris.. 



G. K. G. 



