218 GASTROPODA. [Pectinibranchia. 



1. Anabathron gradatum, Suter, 1908. Plate 13, fig. 7. 

 Andbathron gradatum, Suter, P. Mai. S., viii, 32, pi. 3, f. 33. 



Shell very small, ovate, graduate, rimate, solid, not shining. Sculp- 

 ture consisting of irregular fine axial plications, crossed by fine micro- 

 scopic spiral striae. Colour white. Spire conical, a little higher than 

 the aperture ; outlines convex. Protoconch small, papillate, of 1^ 

 convex and microscopically finely spirally striated whorls. Whorls 4, 

 the last very large, shouldered above, angle not carinated, slightly 

 convex below ; base convex. Suture impressed. Aperture oblique, 

 oval. Peristome continuous, slightly thickened and expanded, sharp, 

 thin on the parietal wall. Columella short and arcuate. Umbilical 

 chink well marked. Operculum unknown. 



Diameter, 1-6 mm. ; height, 2-25 mm. 



Animal unknown. 



Type in my collection. 



Hob. Snares, in 50 fathoms (Captain Bollons). 



Genus 4. KISSOINA, d'Orbigny, 1840. 

 Rissoina, d'Orb., Voy. Amer. Merid., 1840. Type : R. Inca, d'Orb. 



Shell rissoiform, ribbed, cancellated or smooth, whorls numerous, 

 apex mamillated ; aperture semilunar, lip thickened within, a little 

 reflected, anteriorly mostly effuse or faintly channelled ; operculum 

 corneous, thick, semilunar, paucispiral, with a claviform process on 

 the internal face. 



The form of the operculum and effuse character of the base of the 

 aperture are distinguishing features of this group. 



The species inhabit warm and temperate seas, are world-wide in 

 distribution, and over 100 good species have been characterized. 



There are some Secondary and Tertiary species. 



KEY TO SUBDIVISIONS. 



A. Shell axially costate, with or without spiral striae, aperture 



produced . . . . . . . . . . . . RISSOINA. 



B. Upper part of shell axially costate, lower part smooth or 



spirally striate . . . . . . . . . . MCERCHIELLA. 



C. Shell solid, white, polished, smooth or partly striate, outer lip 



thick . . . . . . . . . . . . ZEBINA. 



D. Shell smooth, aperture subcircular, peristome simple, not 



effuse below . . . . . . . . EATONIELLA. 



Sect. 1. RISSOINA, s. str. 



Shell axially costate, with or without spiral striae, aperture produced 

 below, without funicular rib on the base. 



KEY TO SPECIES. 



A. Shell with fine spiral striae, spire twice the height of the aperture. 



a. Height of shell less than 8 mm. 



b. Axial riblets on body-whorl 22 to 25, 67 whorls . . Hartley i. 



bb. Axial riblets on body-whorl 15 to 16, 7-8 whorls . . rugulosa. 

 aa. Height of shell more than 8 mm. Axial ri blots about 14 . . sonata. 



B. Shell without spiral striae, spire more than twice the height of the 



aperture, 5 whorls . . . . . . . . . . rufolactea. 



