LOWER PALEOZOIC GASTEROPODA — ETHERIDQE. 7t3 



Genus Mourlonia, De Koninck, 1883. 

 (Faune Calc. Oarb. Belgique, 1880, pt. 4, p. 75.) 



Mourlonia duni, sp. nov. 

 PL XV., Fig. 5 ; PI. xvi., Fig. 2. 



Sp. char. — Shell conical, or somewhat trochiform, the sides of 

 the cone fairly continuous; spire rather depressed, but acute at the 

 apex ; whorls six, gently rounded ; base convex. Body whorl 

 large, more than twice the height of the penultimate whorl, 

 obtusely angular at the centre ; sutures faintly impressed ; band 

 sutural on all but the body whorl, bounded above by a faint keel, 

 on the body whorl occupying the obtuse median angle, the bound- 

 ing keels very sharp and distinct, with a faintly impressed groove 

 below the lower, and apparently without special sculpture ; sinus 

 unknown ; umbilicus open, although not widely so ; mouth oval, 

 with the inner lip reflected somewhat over the umbilicus, but 

 without concealing it. 



Ql)s. — The late Mr. Felix Ratte figured* three univalves from 

 our Lower Palteozoic rocks without assigning specific names to 

 them, nor even generic in the case of two. Whether or no the 

 present shell be one of these I am in doubt, but in some points 

 his fig. 6 is like it, and again in other respects widely divergent ; 

 for instance in the figure quoted there is too great a convexity of 

 the whorls, too elevated a spire, and too prominent a band. At 

 the same time there is the possibility that the two may be identical, 

 allowing for defective drawing. 



Mourlonia duni is an exceedingly characteristic species of the 

 Wellington Caves Limestone, and is at present unknown to me 

 from any other horizon. It is named in honour of my former 

 Assistant, Mr. W. S. Dun, to whom I am indebted for much 

 cordial help. 



Log and Horizon — Wellington Caves, N. S. Wales. Siluro- 

 Devonian. 



Genus Helicotoraa, Salter, 18.59. 



(Canadian Organic Remains, 1859, Dec. I., p. 10.) 



Helicotoma johnstoni, sp. nov. 



PI. XV., Figs. 6-8; PI. xvi., Figs. 3 and 4. 



Straparollus (Maclurea) tasmanicus, Johnston, Geol. Tas., 1888, 

 t. 5, f. 7 (excl. f. 1 and la). 

 Sp. char.— Shell discoid, of about four whorls, each nearly 

 twice the breadth of the preceding ; spire short, wholly depressed 



* Proc. Linn. Soc. N. S. Wales, x., 1, 1885, t. 9. f. 6. 



