Amphithalamus.] GASTROPODA. 217 



Genus 2. AMPHITHALAMUS, Carpenter, 1865. 



Amphithalamus, Carpenter, A.M.N.H., xv, 1865, 181. Type : A. inclusa, 

 Carp. Scrobs, Watson, 1886. 



Shell pupoidal ; peristome duplicated, the inner lip produced 

 forward, with a subbasal space behind it, outer lip joining it pos- 

 teriorly, suddenly contracted in the adult. 



Distribution. California, Japan, Australasia. 



1. Amphithalamus Hedleyi, Suter, 1908. Plate 13, fig. 6. 

 Amphithalamus Hedleyi, Suter, P. Mai. S., viii, 31, pi. 3, f. 32. 



Shell minute, oval, usually spirally sculptured, pinkish or white, 

 imperforate. Sculpture consisting of fine spiral lines, distant or close 

 together, with a keeled shoulder, and sometimes a cincture margining 

 the suture below ; the shoulder may be ornamented by a few spirals 

 only or by numerous fine spiral threads ; very often the sculpture is 

 becoming obsolete or may be absent altogether, the shoulder only 

 slightly angled. Colour uniformly pink, mostly yellowish-white near 

 the mouth, but sometimes with a light-coloured band below the suture 

 and the base whitish ; white specimens are also met with, on which 

 the spiral sculpture may be pink-coloured. Spire conic, with blunt 

 and rounded apex, a little higher than the aperture ; outlines convex. 

 Protoconch rather large, of 1 flatly convex, smooth whorl, the nucleus 

 large. Whorls 3, convex, the last shouldered ; base convex. Stiture 

 canaliculate. Aperture oblique, ovato-semilunar, extended beyond the 

 body-whorl, and separated from it by a broad white flat and slightly 

 sunken callosity. Peristome very thick and rounded. Columella very 

 short. Operculum unknown. 



Diameter, 0-7 mm. ; height, 1-2 mm. 



Animal unknown. 



Type in my collection. 



Hob. Mafoney's Reef, Hauraki Gulf, type (H. S.) ; Lyall Bay 

 (H. S.) ; Titahi Bay, Cook Strait (Miss Mestayer). 



Remarks. Mr. Hedley has discovered this species also in Australian 

 waters. With regard to sculpture, this is one of the most variable 

 shells known to me ; all intermediate grades between quite smooth 

 and distinctly spirally ridged forms occur, but the peculiarities of the 

 aperture remain constant. 



Genus 3. ANABATHRON, Frauenfeld, 1867. 



Anabaihron, Frfld., " Novara, " Exped., Zool., ii, 1867, 13. Type: Rissoa 

 contabulata, Frfld. 



Shell very small, oblong, thick, smooth, scalariform, with a carinated 

 shoulder, imperforate ; aperture rounded ; peristome continuous. 

 Distribution. Australasia. 



