PLANISPIRA. 287 



The principal features of this little species are its depressed and 

 openly umbilicated form, the strong costulations, and the contracted 

 dentate aperture. The shallow depression upon the upper surface 

 of the last whorl commences behind the peristome, and running 

 parallel to but a little distance from the suture, extends about half 

 way round. The upper margin of the peristome is indented above 

 the conspicuous tubercle, and, between it and the suture is arched, 

 but very little expanded. On the contrary, both in front and at 

 the base, it is more dilated and reflexed. (Sin.) 



P. COLLINGII Smith. PL 58, figs. 10, 11. 



Shell orbicular, depressed, broadly umbilicated, brown above, 

 pallid below, covered with a short-haired epidermis. Whorls 4-5, 

 rather slowly increasing, slightly convex, separated by a profound 

 suture, minutely sculptured throughout with delicate and punctate 

 growth-lines; the last whorl rounded at the periphery, slightly 

 descending in front, lightly impressed above behind the lip. Aper- 

 ture nearly horizontal, rounded-triangular ; peristome narrowly 

 expanded above, the columellar margin broadly reflexed, basal lip 

 subdentate within. 



Alt. 4, greater diam. 10, lesser 8? mill. (Sm.) 



Baudin Island, N. W. Australia (J. J. Walker.) 



Helix ( Gonostoma) collingii E. A. SMITH, The Conchologist, ii, 

 p. 98, figs. 



Shell flatly discoidal, with the spire only very little raised above 

 the body-whorl, rather openly umbilicated, light brown above and 

 pale beneath. When in fresh condition the surface is covered with 

 a thin, shortly pilose epidermis. Worn shells exhibit innumerable 

 minute punctures showing where the short delicate seise have been. 

 Whorls 4, regularly and rather slowly increasing, moderately con- 

 vex, and separated by a deep sutural line ; besides the punctures, 

 exhibiting fine lines of growth ; last whorl rounded at the peri- 

 phery, only very feebly deflexed close to the aperture, and exhibit- 

 ing a slight depression above, about the middle of the upper margin 

 of the peristome. Aperture somewhat triangular in outline but 

 with rounded angles, almost horizontal in position ; peristome nar- 

 rowly reflected above, more broadly expanded along the basal 

 margin, especially over the umbilicus. A conspicuous tubercle or 

 prominence occurs on the inner edge of the basal margin and a less 

 pronounced one within the upper margin corresponding to the 



