162 GASTROPODA. [Aspidobranchia. 



Subgen. 1. MARMOROSTOMA, Swainson, 1840. 

 Type : T. porphyr elicits, Mart. 



Shell depressed turbinate, very solid, umbilicate or imperforate, 

 smooth, lirate or nodulose ; spire depressed, of few whorls ; aperture 

 round, produced but not channelled at base ; operculum circular, 

 nucleus subcentral, outside convex, smooth or granulose ; radula 

 with a reflected simple cusp on the central tooth. 



1. Turbo smaragdus, Martyn, 1784. Plate 40, fig. 7. 



Helix smaragdus, Mart., Un. Couch., ii, f. 73, 74. Turbo smaragdus, Mart.. 

 Man. Conch. (1), x, 217. T. helicinus, Bora. Index Mus. Cses. Vindob., 

 1778, 355 ; not of Phipps, Voy. North Pole. 1774, 193. T. smaragdus, 

 var. tricostatus, Hutton, P.L.S. N.S.W., ix, 1884, 355; Snter, T.N.Z.I., 

 xxxviii, 323. T. (LuneUa) radina. Webster. T.N.Z.I., xxxvii, 1904 

 (1905), 276, pi. 9. f. 1. 



Shell rather large, heliciform, imperforate. Sculpture : The first 

 few whorls with small spiniform projections above the suture, on ;> 

 narrow, slightly projecting ledge, which with further growth of the 

 shell forms a smooth ridge, margining the suture. The second, third, 

 and sometimes the fourth are spirally ribbed ; there is 1 rib on the 

 earlier whorls, 3 on the fourth, followed by 2 low spiral ribs upon 

 the base ; this ornamentation is lost with further growth, the whorls 

 becoming smooth ; adult shells very seldom show any trace of sculp- 

 ture, except strong oblique growth-lines and subobsolete spiral sulci, 

 the whole of it being obliterated by erosion. Colour greenish-black. 

 Epidermis thick, black, dull ; beneath it the shell is green. Spire 

 conoidal or conical, outlines convex, always lower than the height of 

 aperture. Protoconch of H whorls, depressed, white, smooth, mostly 

 much eroded. Whorls 4 to 5, rapidly increasing, convex, the last large, 

 depressed above and more or less concave below the suture ; base 

 flatly convex. Suture not deep. Aperture large, rounded, oblique, 

 pearly- white within. Outer lip sharp, strongly convex, black-edged . 

 and with a broad white callous band inside. Columella subvertical, 

 strongly concave, smooth, white above, pearly at its base. The inner 

 lip broadly spread out as a thick white callus over the excavated 

 umbilical area, edged with light yellow or orange down to the base, 

 and uniting the margins by a broad, thin, and widespread callosity. 

 Operculum flat inside, with 4 to 7 whorls, the nucleus more than one- 

 third the distance across the face ; outside deep green, except on the 

 side of increment, which is white ; very minutely remotely granose. 



Diameter, 50-60 mm. ; height, 40-50 mm. Diameter, 70 mm. ; 

 height, 73 mm. (my largest specimen). 



Denttiion.--Tioschel, Das Gebiss d. Schnecken, vol. ii. pi. 19, f. 1 ; 

 Hutton, T.N.Z.L, xiv, 165, pi. 7, f. G. 



Animal Hutton, T.N.Z.L, xiii, 202. 



