1571.] MR. HARPER PEASE ON POLYNESIAN LAND-SHELLS. 469 



As the two species have been confounded by many collectors, I 

 furnish a detailed description of each, drawn up from mature speci- 

 mens, of which I have had an opportunity of examiuing a large 

 number. 



Plecotrema striata, Phil. 



Auricula striata, Phil. Zeit. f. Mai. 1846, p. 98. 

 Plecotrema striata, Pfr. Mon. Auric. 1856, p. 104. 



T. crassa, imperforata, globoso-conica, subovata, nigra, spiraliter 

 impresse striata, striis rare incequaliter distantibus, interstitiis 

 plants, st?'iis remote hispidulis ; spira conica, mucronata, con- 

 vexiuscula ; sutura linearis; anfr. 7, ultimus tumidiusculus , \ 

 longitudinis testa fere aquans, basi vix attenuatus ; aperlura 

 fere verticalis, oblonga, postice acuta, vix contracla, basi i'otun- 

 data, nigricans vel cinereo-nigrescens ; plica parietales 2, lamel/i- 

 formes, superior per obliqua, altera extus bifida, vulde compressa, 

 elevata, profunde intrans ; plica columellaris valida, transversa ; 

 peristoma rectum, acutum, marginibus plerumque callo lato tenuis- 

 simo junctis, dextro intus, dimidio anteriore et circa basin prope 

 marginem calloso, bidentato ; columella extus ad marginem vix 

 elevato-laminata, infra juxta regionem umbilicalem viv crispata. 

 Dimens. 8 X 5, vel 5 X 3 mill. 

 Hab. Insula Oahu. 



This species is constant in its characters, and distinct from all 

 varieties of P. clausa, H. & A. Ad. ; the shell is black, solid, engraved 

 concentrically with impressed striae, which are generally regular ; 

 but occasionally one is omitted, leaving the interspaces wider ; the 

 interstices are flat ; the last whorl is swollen, about one half the 

 length of the shell ; the aperture is very slightly oblique, acute poste- 

 riorly, more so than in P. clausa, and in some specimens constricted, 

 caused by a depression around the upper part of the last whorl near 

 the suture ; the lamellae on the inner lip are oblique, more compressed 

 and prominent than in P. clausa, the lower one especially, which 

 passes round far within the aperture ; the outer lip on its edge is 

 acute, on its anterior half and around the base, just within the mar- 

 gin, it is slightly callous, on which part the teeth are placed, which 

 are smaller than those in P. clausa. The columella is bordered by 

 an elevated lamina ; the aperture is blackish or dark cinereous ; the 

 teeth and lamellae white ; the striae are furnished with remote bristly 

 hairs. The characters by which the above may be readily distin- 

 guished from P. clausa are its black colour, larger size, dark aper- 

 ture, not being ribbed or Urate but striate, the aperture being more 

 open, the lamellae on the wall of the aperture compressed and pro- 

 minent, the teeth on outer lip smaller and the callosity not so thick. 

 These characters are constant, even in specimens of the smallest size. 



Plecotrema clausa, A. Ad. 



T. imperforata, ovato-conoidea, crassa, vix nitidula, spiraliter costu- 

 lata aut lirata, costis rotundatis, interstitiis sctulis munitis et Ion- 



