- 353 — 



zontal fold whicli in P. tennis is free, is hère united to the 

 lower extremity of the anterior vertical plate ; while the 

 upper horizontal fold is shorter and more distant froni the 

 anterior plate. The paraliel ridge ou the posterior side of 

 the anterior plate is possibly the reraains of an earlier set 

 of barriers, judging from an analogous case observed in 

 a spécimen of P. Giardi. The shell is larger and more solid 

 than P. tennis \ the spire is more elevated, the last whorl 

 more deflexed in front and the aperture is moredilated. 



The duplication of the second, third, fourlh, and fifth pal- 

 atal folds is a feature not before observed by me in Tonkin 

 species, and know^n only in the Section Endothyra, where 

 it occurs in most of the species. The second fold has simp- 

 ly anelongated denticle posteriorly, but the third, fourth, 

 and fifth hâve each, besides the smaller lov^ paraliel ridge, 

 a heavy deposit of callus in the sinus formed by their two 

 extremities, a feature difficult to show in the diagram. 

 I was at first inclined to cousider thèse accessory bar- 

 riers as remains of an earlier séries, but in a second 

 spécimen which appears to be not quite mature the ante- 

 rior barriers are not so much developed as those in the 

 type, while the poslerlor séries is still more rudimentary, 

 pointing to the probability of Iheir being of niore récent 

 origin. Tliis view dérives further support from the prés- 

 ence of the ridges posteriorly to the third and fourth 

 plates in P. soror [mde infra) and the four posterior 

 denlicles in P. Mansuyi, ail which structures I regard as 

 homologous to those in the présent species. 



PlECTOPYLIS SUPRAFILARIS n. Sp. 



(l'I. VII, fi?. 7, 8, 9) 



Testa dextrorsa, modicc umbilicata, discoidea, corneo-fulva. 

 Spira depresso-conoidea, apice prominulo. Anfr. 7 regulariter 

 crescentes^ sutura parum prufunda jmicti, primus lœvis, se- 



