654 GASTROPODA. [Pulmo; 



2. Serpho Matthews!, Suter, 1909. Plate 26, fig. 1. 



Serpho Matthewsi, Sut., P. Mai. S., viii, 1909, 259, pi. 11, f. 19. 



Shell small, turbinate, perforate, thin and fragile, radially ribbed, 

 not shining. Sculpture consisting of fine, inequidistant, retractive, 

 flexuous radial riblets on the post-nuclear whorls, extending on the 

 base down to the perforation, their number being 6-8 per millimetre ; 

 all whorls have fine and dense microscopic spiral strife, passing over 

 the riblets and decussating the fine growth-lines of their interstices. 

 Colour : Protoconch light-yellowish with arcuate radial fuscous streaks, 

 which are sometimes present on the next volution, but then get obso- 

 lete, giving place to a uniform light-brown colour, interrupted only by 

 a whitish band below the suture, and a white central disc on the base ; 

 riblets white. Epidermis thin, dull. Spire elevated, conoidal, apex 

 rather blunt, outlines somewhat convex, its height the same as that 

 of the aperture. Protoconch of If convex whorls, the nucleus very 

 little convexly raised. Whorls 4 to 5, regularly increasing, convex, 

 periphery of body-whorl regularly arched ; base rounded. Aperture 

 oblique, lunate. Peristome simple, sharp. Columella short, slightly 

 arcuate. Inner lip lightly callous, reflexed above and partly covering 

 the distinct narrow perforation, spreading broadly as a thin shining 

 glaze over the parietal wall. 



Diameter Maj., 7-5 mm. ; min., 6-7 mm. : height, 6 mm. 



Animal unknown. 



Type in my collection. 



Hob. Kaitaia. North Island (R. H. Matthews). 



Genus 7. THERASIA. Hutton, 1883. 

 Therasia, Hutt., N.Z.J.S., i, 1883, 477. Type : T. Thaisu, Hutton. 



Animal elongated ; mantle subcentral, included ; foot long and 

 narrow, reaching beyond the shell, rounded behind, slightly truncated, 

 and with a mucous gland situated under a caudal papilla. 



Jaw membranous, arcuate or horseshoe-shaped, with broad imbri- 

 cating plates. 



Dentition : Central teeth narrow, with small reflection, the meso- 

 cone long, ectocones hardly visible. Lateral teeth with larger reflec- 

 tion, the inner ones without side cusps, the outer tricuspid. Marginal 

 teeth multicuspid, very variable. 



Shell depressed, perforate or umbilicate, thin, with conoidal spire ; 

 the periphery angular or subangular ; aperture round-lunar ; lip thin, 

 slightly reflexed at the columella ; surface striated ; protoconch spirally 

 striated. 



Resembles Allodiscus in the dentition and the spirally striated apex 

 of the shell, but differs in the form and sculpture of the latter, which is 

 much more as in Thalassohelix. 



Distribution. New Zealand . 



