£05 



Notes on South Australian Marine Mollusca, 

 WITH Descriptions of New Species. -Part VM. 



By Jos. C Verco, M.D., LoncL, F.R.C.S., Eng., Etc. 



Plate XXIX. 



[Read September 3, 1907.] 



Cyclostrema homalon, n. sp. PI. xxix., tigs. 3, 4, 



Shell small, thin, ilatly depressed, of 4^ whorls. Apical 

 whorls convex smooth. Spire whorls tlat excavafcely sloping 

 towards the upper suture, rounded towards the lower, with a 

 spiral near the upper suture, which is well adpressed so as to 

 simulate another spiral, and two near the lower suture. 

 Body whorl large, with about seven spirals, the lowest form- 

 ing a basal carina, starting where the inner lip joins the 

 body whorl at its base, and ending at the outer third of the 

 basal lip. Umbilicus large and perspective, with about ten 

 spiral lirae. There is a smooth area between the outermost 

 and the basal carina. The aperture is quadrate, with round- 

 ed angles, and lies in an oblique vertical plane. The labrum 

 is excavated at a little distance from the suture, then pro- 

 jects curvedly forwards, and then continuously retrocedes. 

 The inner lip is applied to the base, so that the aperture is 

 not quite circular or complete. Very fine crowded axial 

 microscopic markings, which do not follow the sinuosities of 

 the outer lip. 



Dim. — Largest diameter, 2'7 mm. ; smallest, 2 mm. ; 

 height, 1 mm. 



Diagnosis. — C. harriettce^ Petterd, is closely allied, but 

 has a less open umbilicus, and its labrum is not sinuous on 

 the dorsum, but has a continuous convex curve; and the intra- 

 umbilical spirals are much finer and more crowded. 



Variations. — One variety attains a size of 4"1 mm. in 

 diameter, and is more solid. Its aperture is rounder; the 

 umbilicus wider and more perspective, is radially wrinkled, 

 and may not have so many spiral lirae. There may be no 

 spiral lira near the suture on the whorls, nor any elsewhere, 

 or there may be several on the sides of the body-whorl. Some 

 show the basal carina distinctly, others feebly, and others 

 not at all; but the sinuosity of the lip is present and the 

 miscroscopic radial markings. 



Locality. — Type, 62 fathoms north-west of Cape Borda ; 

 var., 130 fathoms, Cape Jaffa. 



