Monodonta.] GASTROPODA. 117 



Type (?). 



Hob. Throughout New Zealand ; Chatham and Auckland Islands. 

 Brought to England by Captain Cook. 



This is the most common species of the genus. 

 Fossil in the Pliocene. 



4. Monodonta atrovirens, Philippi, 1851. Plate 38, fig. 6. 



Trochus atrovirens, Phil., Conch. Cab., 148, pi. 24, f. 12. Monodonta atro- 

 virens, Phil. : Fischer, Coq. Viv., 373, pi. 114, f. 1 ; Man. Conch. (1). xi, 

 110, pi. 22, f. 48-50 ; Sxiter, P. Mai. S., ii, 263. 



Shell orbiculate-conoidal, solid, imperforate, greenish-black. Sculp- 

 ture consisting of spiral narrow sulci, 7 to 9 on the penultimate whorl, 

 the flat cinguli crossed by close and fine lines of growth ; base with 

 about 7 sulci, a little closer together: Colour greenish-black, very 

 often with irregularly scattered yellowish dots. Epidermis shining, 

 often eroded on the spire, but seldom rubbed off. Spire depressed 

 conoidal, sides very convex, apex sharp. Protoconch conic, small, of 

 2^ smooth whorls. Whorls 6, rapidly increasing, slightly convex and 

 depressed above, last whorl rounded at the periphery ; base flatly 

 convex. Suture impressed, margined below by a cingula much broader 

 than the succeeding ones. Aperture subrhomboidal, pearly and lirate 

 within. Outer lip convex, sharp, black-edged, then a broad silvery 

 band, often followed by a broad white and opaque callosity. Columella 

 oblique, nearly straight, nodulous at the base, the callus extending on 

 the inner side of the basal lip. Inner lip broadly expanded, bounded 

 by green or blackish-green ; a distinct tongue-shaped pit at the centre 

 of the umbilical tract, extending downward to the basal lip. 



Diameter, 14-23 mm. ; height, 9-17 mm. 



Dentition unknown. 



Type (?) 



Hob. Tasman Bay (type) ; Hauraki Gulf (H. S.) ; west coast of 

 the North Island ; Lyall Bay (H. S.) ; Te Onepoto, near Lyttelton 

 (H. S.) ; St. Clair, near Dunedin (H. S.). 



Remark. This species is very nearly allied to M. morio. 



5. Monodonta corrosa, A. Adams, 1853. Plate 38, fig. 7. 



Labio corrow, A. Ad., P.Z.S., 1851 (1853). 180. Diloma corrosa. Ad. : 

 Hutton, M.N.Z.M., 96. Monodonta melanoloma, Menke, Man. Conch. 

 (1), xi, 104, pi. 22. f. 56, 57 ; Suter, P. Mai. 8., ii, 266. not of Menke. 

 Trochus labio, L. : Chemnitz, Siidland. Conch., 199, not of Linnaeus. 



Shell globose-conical, solid, imperforate, surface dull, corroded. 

 Sculpture consisting of subobsolete spiral cinguli, about 6 on the 

 penultimate-whorl, about 7 on the base, much closer together ; the 

 whole surface with oblique subobsolete growth-strise. Colour dark- 

 purplish, overlaid by a more or less eroded yellowish-white layer, 

 leaving sometimes zigzag bands of purple on the last whorl. Spire 

 conic, apex much eroded. Whorls about 5, slightly convex, the last 



