"224 RETUSA. 



R. AMPHIZOSTUS Watson. PL 21, fig. 4. 



Shell small, rather broadly cylindrical, but contracted in the 

 middle, and broadest below the contraction, very bluntly rounded 

 in front, longitudinally striate and very finely spiralled, with a flat 

 but slightly depressed crown and a small papillary apex. Sculp- 

 ture : Longitudinals there are a great many small hair-like ridges 

 and furrows on the lines of growth ; they are nowhere strong, but 

 are feeblest on the base. Spirals the whole surface is very equally 

 striated, with delicate shallow scratched lines parted by flat sur- 

 faces four or five times the width of the lines ; there is a very 

 slight and gradual constriction most apparent near the outer lip 

 about the middle of the body, and in front of this the shell is 

 slightly tumid. Color translucent white, with vague trace of spiral 

 bands. Mouth the full length of the shell ; shaped like a racket, 

 being oval in front, long and narrow above ; it is small and rounded 

 at the top, which just rises to the crown. Whorls 4, of which only 

 the small rounded tops are seen on the crown, where, they are 

 slightly and radiatingly ridged, the last envelopes all the others. 

 Suture impressed and distinct. Outer lip rounded at the top where 

 it does not rise above the crown ; it runs straight and parallel to the 

 inner lip till below the middle where it bends outwards in exact 

 symmetry with the corresponding bend of the inner lip on the base, 

 forming a very regular oval curve in front ; the edge line is regu- 

 larly curved, retreating slightly behind and in front, and advancing 

 in the middle where the lip is contracted. Top flat, but slightly de- 

 pressed, with a small papillary apex in the middle, the outer edge 

 is roundly angulated. Inner lip straight down the body, concave 

 on the pillar, which has a very slight twist and a narrow patulous 

 edge, behind which is a scarcely appreciable umbilical depression ; 

 the point of the pillar projects in front clear of the sweep of the 

 basal curve. Alt. 0'12 in., diam. 0*06. Breadth of mouth at same 

 place, 0-02 inch (Fate.). 



Near Cape York, N. E. Australia, 6-8 fms. (Chall.). 



Utriculus amphizostus WATS., J. L. S. L. xvii, p. 336 ; Chall. 

 Gastr. p, 652, pi. 48, f. 11. 



This species is very like Utriculus truncatulus (Brug.) ; but that 

 has much stronger longitudinals, no spirals, and an oblique crown, 

 sloping down from left to right on which side the top of the mouth 

 and outer lip rise in a rounded loop very considerably above the top 

 -of the body whorl ( Wats.). 



