98 MONODONTA. 



Hutton and others is a distinct species. A notable character of this 

 species is the band of iridescent nacre which connects the termina- 

 tions of the peristome, extending across the parietal wall. 



M. CRUSOEANA Pilsbry. PL 35, figs. 19-21. 



Shell similar in form to M. nigerrima or somewhat more depressed ; 

 the color, columella and parietal wall as in M. nigerrima ; Outside 

 closely conspicuously spirally lirate, the sutures bordered below by a 

 depression or groove ; outer lip acute, thin, very narrowly black- 

 edged, bordered within by a broad band of very thin white sub- 

 stance, which overlies the nacre ; parietal wall with a band of nacre 

 connecting the ends of the peristome, but obscured by the same thin 

 opaque layer ; fauces brilliantly iridescent ; lip lirate within ; upper 

 angle of the aperture narrowly channeled ; ribs of the outer surface 

 about 8 in number on the penultimate, 20 (more or less) on the 

 last whorl. Alt. 15, diam. 17 mill. 



Ins. Juan Fernandez ; Coquimbo, Chili 



Two trays of this well-marked form are before me. It is need- 

 less to compare with the Australo-Zealandic species, for the band of 

 nacre across the parieto-columellar region, connecting the termina- 

 tions of the peristome, at once separates our species from these, and 

 allies it to M. nigerrima, the only other form exhibiting this char- 

 acter. From M. nigerrima it is separated by the much stronger 

 liration of the entire surface, and the canaliculation of the sutures. 



Section NEODILOMA Fischer, 1885. 



Neodiloma FISCHER, Manuel de Conchyliologie, p. 820. 



Differs from typical Diloma principally in its Australasian dis- 

 tribution. The dentition also differs somewhat from Diloma. (PI. 

 50, fig. 12, NeodiloiiKi <rf]ilops Gmel.) 



M. ^THIOPS Gmelin. PI. 19, figs. 99, 100 ; pi. 20, fig. 19. 



Shell imperforate, globose-conoid, solid, thick, blackish, encircled 

 by series of narrow white marks, formed by the interruption of nu- 

 merous longitudinal white lines by narrow spiral black stripes ; spire 

 conic, whorls 5, convex, the first eroded, spirally sulcate, the last 

 marked by narrow, separated spiral grooves, the cuticle lamellose- 

 striate ; base convex, eroded and subconcave in front of the aperture ; 

 aperture large, oblique, expanded ; outer lip black-edged, then thick- 

 ened with opaque white; columella short, obtusely bidentate, the 



