— 348 — 



Altlîough I do not feel inclined to base a new species on 

 this single spécimen, otherwise undistinguishable from 

 P. Giardi, the above noled déviations from the normal 

 structures are so considérable tbat I bave thougbt it 

 advisable to give illustrations of them. The same spéci- 

 men possesses an older set of barriers under the parié- 

 tal ridge of the aperture. This conforms in every respect 

 to the later séries ; the pariétal barriers are slightly atte- 

 nuated, but the palatal folds are already much disinte- 

 grated ; in this respect it therefore accords with the case 

 cited above for the var. minor. 



Plectopylis Mansuyi n. sp. 



(PI. VII, fig. 1, 2, 3). 



Testa parva, dextrorsa, late umbilicata, discoidea, sub- 

 translucens, plus minnsve intense fuscescens. Spira depressius- 

 cula, apice prominulo. Anfr. 6-6 ij^ concexi, lente et regula- 

 riter crescentes, sutura impressa juncti ; primi lœves, 7iitidi, 

 sequentes costulati, ultimus inferne minute striatus, ac supra 

 peripheî'iam subangulatus^ inferne lœviter compressus, circa 

 umbilicum obtuse angulatus, prope aperturam paululum dila- 

 tatus, mxdescendens. Apertura obliqua^ subauriculata. Péris- 

 toma albidum vel lividum, paululum dilatatum, valde reflexujn, 

 marginibus callo crassissimo plicam obliquant praebente, 

 junctis. 



Laminse pariétales 2 verticales, antica hreviore, flexuosa, 

 postica incurvata. Laminse palatales 5, callo verticali junctse : 

 prima {prope suturam) minima, fere horizontalis , sequentes 

 S semicirculares, subœquales, obliquse, postice lœviter denti- 

 culatx. 



Shell dextral, widely umbilicated, discoid, almost trans- 

 parent, from pale to ruddy corneous, the nepionic whorls 

 smooth, shiuiog, the later ones duU, finely and regularly 

 ribbed above, the riblets ceasiug at or near the periphery, 



