158 GASTROPODA. [Aspidobranchia. 



also with blunt, curved, delicately serrate tips, beyond which is a 

 series of numerous (between 30 and 50) long, very slender, some- 

 what sickle-shaped hooks, sometimes with delicately serrate tips. 



Shell small, thin, of rather delicate texture, opaque white, slightly 

 lustrous, of few convex whorls, forming an elevated spire, with rela- 

 tively large prominent nuclear whorl and large body-whorl. Suture 

 deep. Umbilicus small, deep, not showing any whorls. Aperture 

 somewhat oblique, circular, with a slight sutural angle, not modified by 

 the body-whorl, to which the simple, continuous peritreme is but 

 slightly attached, often having an indistinct thread just within the 

 inner lip, fading out above and below, so that it extends but about 

 half-way round the aperture ; it is much nearer the edge along the 

 columellar margin than at the ends, and is evidently to prevent the 

 thin operculum being drawn in too far. The operculum is circular, 

 thin, of a delicate horn-colour, with central nucleus, of about 7 whorls, 

 defined by a distinct spiral thread ; often showing delicate microscopic 

 transverse growth-lines. 



KEY TO SPECIES. 



a. Sculpture consisting of microscopic spiral striae only . . . . micro. 



b. Sculpture consisting of radiate riblets and microscopic spiral strife . . condum. 



1. Lissospira corulum, Hutton, 1885. Plate 34, fig. 6. 



Scalaria condum, Hutt., T.N.Z.I., xvii, 1884 (1885), 322, pi. 18, 1. 22 .(main) ; 

 Hutt,, Plioc. M., 67, pi. 8, f. 72. Scala corulum., Hutt. : Suter, T.N.Z.I.. 

 xxxix, 267. Cydostrema corulum, Hutt, : Suter, P. Mai. S., viii, 24 : 

 Iredale, T.N.Z.I., xl, 382. 



Shell minute, elevated turbinate, perforate, translucent, white, 

 shining. Sculpture consisting of fine equidistant radiate riblets, 

 about 28 on the last whorl, the interstices finely, microscopically 

 spirally striate. Colour white. Spire conical, higher than the aper- 

 ture, outlines convex. Protoconch small, globose, of 1 smooth whorl. 

 Whorls 5, rather rapidly increasing, convex, the last with the peri- 

 phery and base rounded. Suture deep. Aperture roundly ovate, 

 angled above. Peristome continuous, sometimes thickened by a 

 radiate riblet. Columella arcuate, very little expanded. Perforation 

 narrow, partly hidden by the columella. Operculum not seen. 



Diameter, 1 mm. : height, 1-5 mm. 



Animal unknown. 



Type, from the Pliocene, in the Canterbury Museum, Christchurch. 



Hab. Titahi Bay, Cook Strait, in sand (Miss Mestayer) ; Lyall 

 Bay ; Te Oncpoto, Lyttelton. 



Remark. - - Cydostrema Angeli, T.-Woods ; C. conica, Watson ; 

 and C. crebresculptum, Tate, are very nearly allied species. 

 Fossil in the Pliocene. 



