HELIX-HELENOCONCHA. 91 



H. aorangi SUTER, Tr. N. Z. I. 1889, p. 223, t. 14 f. 5a-c. 

 Maoriana aorangi SUT., 1. c. 1891, p. 300, t. 23, f. 51, 52 (jaw and 

 dentition.) 



Closely allied to M. microundulata, but larger, more globose, with 

 stronger, more distant ribs. The laminae of the aperture are nearly 

 equal in the two species, but M. aorangi has only nine lamellae upon 

 the palatal wall. 



Section HELENOCONCHA Pilsbry. 

 P. BILAMELLATA Sowerby. PL 36, fig. 12. - 



Shell orbiculate-depressed, the spire flat ; whorls 7, the last swollen 

 below, angular above. Umbilicus small. Aperture semilunar, 

 angulated at the upper outer part, the outer lip thin ; inner lip 

 bearing two spiral folds, the posterior one larger. 



Alt. 31, diam. 81 mill. (Sowb.~) 



Between Jamestown and Longwood, along the path, and at the 

 north end of the island, St. Helena. 



H. bilamellata G. SOWERBY, append, to Darwin's Geol. Obs. on- 

 Volcanic Is., p. 157. FORBES, Journ. Geol. Soc. Lond. viii, p. 199, 

 t. 5, f. 8 (1852). Patula bilamellata WOLLASTON, Test. Atlant., p. 

 537. Patula bilamellata var. unilamellata SMITH, P. Z. S. 1892, p. 

 262, t. 21, f. 5. (Not H. bilamellata PFR., Zeitschr. f. Mai. 1845, 

 p. 84; Couchyl. Cab., t. 101, f. 16-18; Monographia i, p. 188.) 



The spire is flat, and marked with irregular reddish rays. 



Var. unilamellata Smith. Aperture with the lower parietal 

 lamella wanting. 



Sugarloaf Ridge, St. Helena. 



P. VERNONI Smith. PI. 36, figs. 13, 14, 15. 



Shell narrowly perforated, depressed discoidal, flattened above, 

 acutely carinated at the periphery, white, radiated with rufous above 

 and beneath ; whorls 6, slowly increasing, slightly convex, striated 

 with delicate growth-lines ; the last whorl acutely carinated, slightly 

 compressed above and below the carina, hardly descending in front, 

 painted below with undulating rufous rays, delicately radiately 

 striated. Aperture small, subrhomboidal, provided with a delicate 

 entering parietal lira ; peristome simple, thin, slightly thickened to- 

 ward the umbilicus. 



Alt. 4, greater diam. 12, lesser 11 mill. (Sm.) 



Side Path, St. Helena (extinct.) 



