HELIX-THERSITES. 91 



low the keel. In front the whorl descends a little below the keel of 

 the preceding one. Aperture very oblique, triangular, bluish-white 

 inside ; peristome thick, dark brown, upper margin expanded, basal 

 and columellar margins reflexed, the latter closing the umbilical 

 perforation. 



Alt. 35, greater diam. 50 mill. 



Alt. 32, greater diam. 52 mill. 

 Richmond River, N. S. Wales; Albert River and Muggerabaa, 



Queensland, Australia. 



H. Richmondiana PFR. P. Z. S. 1851, p. 252 ; Monographia iii,p. 

 178 ; Conchyl. Cab., p. 371, t. 140, f. 3, 4. REEVE, Conch. Icon., f. 

 365. Cox, Monog. Austr. Laud. Sh., p. 62, t. 8, f. 5, 6. HEDLEY, 

 Proc. Roy. Soc. Queensland v, 1888 p. 62 ; and Tkersites Richmon- 

 diana Pfr. HEDLEY, 1. c. vi, 1889, p. 62, plate 3. (Anatomy.) 



There is a light yellowish or reddish variety, with the suture and 

 cariua edged by dark brown bands, the peristome and a small um- 

 bilical patch also dark brown. It may be called forma decolorata. 



The microscopic wrinkles are usually but not always obsolete on 

 the upper surface. The basal lip often has a callous swelling where 

 it joins the short subvertical columellar insertion, corresponding to 

 the callous on this part in the H. novcehollandice. 



H. NOV^HOLLANDIJ^ Gray. PL 13, figs. 51, 52 ; pi. 4, figs. 24, 25. 



Shell lens-shaped or trochiform, carinated at the periphery, the 

 base quite convex ; imperforate. 



Moderately solid, opaque, chestnut-brown, with narrow bands a 

 little lighter on the carina, surrounding the umbilical dark tract, and 

 bordering the dark margin below the suture ; there is also a darker 

 band just above the keel. Surface slightly marked by growth-lines, 

 and showing under a lens a very beautiful pattern of fine, close, 

 wavy wrinkles, covering the surface both above and below ; these 

 wrinkles are usually cut more or less into granules, and on the base 

 are very irregular. The spire is scarcely more convex than the base, 

 conoidal, apex obtuse, sutures scarcely impressed. Whorls about 5, 

 almost flat, the last acutely keeled, the keel becoming more obtuse 

 on the last half of the whorl, which is there more gibbous beneath ; 

 often there is a slight furrow parallel with the keel just below it on 

 the latter part of the last volution. In front the whorl abruptly de- 

 scends below the carina of the preceding whorl. Aperture subtri- 

 angular, purplish inside, very oblique ; peristome dark brown, upper 

 margin expanded, a little sinuous and often toothed just above the 



