116 GASTROPODA. [Aspidobranchta. 



KEY TO SPECIES. 

 A. Whorls spirally sulcate. 



a. Columella backed by a distinct pearly band. 



b. Spiral grooves distant, intervening tracts often reticu- 

 lated with black and white . . . . . . cethiops. 



bb. Spiral grooves close together, 7-10 on the penultimate 



whorl, 

 c. Shell black, dull, with irregularly scattered white 



spots . . . . . . . . . . morio. 



cc. Shell greenish-black, shining, sometimes with 



yellowish spots . . . . . . . . atrovirens. 



aa. Pearly band wanting, or very short and but slightly iri- 

 descent. 

 b. Last whorl carinated, base concave . . . . excavate. 



bb. Last whorl rounded, base flat . . . . . . corrosa. 



B. Whorls spirally ridged. 



a. Spiral ridges nodulous, 3 on the penultimate whorl. Colour 



blackish, with whitish spots on the ridges . . . . litgubris. 



aa. Spiral ridges subnodulous, 3-5 on the penultimate whorl. 



Colour yellowish, with oblique radiate purple lines . . subrostrata. 



3. Monodonta aethiops, Gmelin, 1790. Plate 39, fig. 3. 



Turbo (vthiops, Gmel.. Syst. Nat., ed. xiii, 3596. Monodonta cethiops, GmeL, 

 Man. Conch. (1). 3d, 98, pi. 19. f. 99, 100; pi. 20, f. 19: Suter, P. Mai. 

 S., ii. 262. Trochits zelandicits, Q. & G., Voy. Astrol., Zocl., iii, 1834, 

 257, pi. 64, f. 12-15. Monodonta retic-ularis. Gray, Wood's Suppl., f. 21. 

 ?Labio concolor. A. Ad.. P.Z.S., 1851, 180. 



Shell imperforate, globose - conoid, solid, thick. Sculpture con- 

 sists of distant narrow spiral grooves, the intervening tracts orna- 

 mented with close, fine, oblique, laniellose, radiate striae. Colour 

 blackish or greenish, usually encircled by series of narrow white marks, 

 formed by the interruption of numerous longitudinal white lines by 

 narrow spiral black stripes. Epidermis lamellose. Spire conic, with 

 the apex rounded. Protoconch mostly eroded, spirally lirate, flatly 

 convex. Whorls 5, convex, rapidly increasing ; base convex, eroded 

 and subconcave in front of the aperture. Suture impressed, linear. 

 Aperture large, oblique and expanded, pearly, lirate. Outer lip regu- 

 larly convex, sharp, with a black edge, often spotted with white ; then 

 bounded by a rather broad pearly band, and this is followed by a 

 broad opaque white callosity. Columella short, concave, white, ob- 

 tusely bidentate at the base. The umbilical tract is very broad, sub- 

 concave, bounded on the outer lower margin by a dark-brown streak. 

 The pearly band of the outer lip is continued over the parietal wall to 

 the middle of the umbilical tract, sometimes continuous with the pearly 

 band of the basal lip, forming a complete circle. 



Diameter, 25-30 mm. ; height, 25-33 mm. Diameter. 26 mm. : 

 height, 25 mm. (specimen from Kawhia). 



Dentition. Troschel, Das Gebiss d. Schnecken, ii, pi. 23, f. 3 ; 

 Hutton, T.N.Z.I., xv, 125, pi. 15, f. A ; Man. Conch. (1), xi, pi. 50, f. 1 



