HELIX-HADRA. 181 



A shell of anomalous characters. In referring it to Xanthomelon 

 I have been guided by a certain resemblance to H. nigrilabris in 

 aperture and sculpture. 



H. NULLARBORICA Tate. PI. 40, figs. 96, 97. 



Shell narrowly umbilicated, globosely conic, very thick, surface of 

 a dirty white color, coarsely and closely wrinkled transversely, in- 

 terrupted by equidistant incised lines, whorls 4J , rotund, and just 

 perceptibly flattened at the suture, which is impressed. Last whorl 

 somewhat inflated, descending but little in front, base convex. Ap- 

 erture oblique, subcircular, peristome sub-acute, slightly reflected, 

 margins joined by a callus ; columella margin thickly dilated above 

 and nearly covering the umbilicus. 



Animal. Foot brownish-grey, muzzle black with white spots, 

 tentacles black, collar grey and creamy white. 



H. Nullarborica has considerable resemblance to H. Angasiana, 

 differing from it, irrespective of coloration, in its more globose form, 

 minute umbilicus, in its wrinkled surface, and longitudinally im- 

 pressed lines and in the callus covering on the pillar. 



The ridges of growth of the shell of H. Angasiana are regularly 

 curved, and are interrupted by close set striae, giving rise to a gran- 

 ulated appearance under the lens; but in H. Nullarborica they are 

 wavy and varied in the degree of coarseness, whilst the incised lon- 

 gitudinal lines are distant from 20 to 25 on the body-whorl, and 

 help to give that pitted appearance to the shell which is observable 

 by the unaided eye. The shell is moreover remarkable for its ex- 

 cessively thick test, for its semi-fossilized aspect, and is devoid of an 

 epidermis. It is very constant in form and color, though in size it 

 presents great differences ; the dimensions given are those belonging 

 to a specimen of the common size. I may add, to avoid misapprehen- 

 sion on the subject, that I gathered many living examples. ( Tate.) 



Alt. 18, greater diam. 18, lesser 16 mill. 



Bunda Plateau, extending to the scrubby sandhills on its east, and 

 to the Roe Plains at the foot of the Hampton Range, in Western Aus- 

 tralia. 



H. nullarborica TATE, Trans, and Proc. and Rep. Philos. Soc. 

 Adelaide, S. Austr., 1878-9, p. 133, t. 5, f. la, Ib. 



The specific name is adopted from that of the treeless portion of 

 the Bunda Plateau known as the Nullarbor Plain. (Tate.} 



