GASTROPODA. [Aspidobranchia. 



Hal. East and west coast of the North Island : Hauraki Gulf, 

 East Cape, Hokianga, Manukau Heads, Cook Strait, Bay of Islands. 

 South Island : Banks Peninsula (Iredale). Chatham Islands. 



2. Cantharidus opalus, Martyn, 1784. Plate 8, fig. 10. 



Umax opalus, Mart,, Un. Conch., i, fig. 24, not of 1769. Cantharidus 

 opalus. Mart. : Hedley, Colon. Mus. Bull., i, 1906, 49. Trochus iris, Gmel., 

 Syst, Nat., ed. xiii, 1790, 3580. Cantharidus iris, Gmel., Man Conch 

 (1), xi, 122, pi. 34, f. 15; -Siiter, P. Alwl. S., ii, 268. C. zealandicus, 

 A. Ad., P.Z.S., 1851, 169. 



Shell imperforate, elevated conical, angular at the periphery, 

 solid, but not very thick. Sculpture consisting of spiral grooves, about 



7 on the penultimate whorl, mostly indistinct, crossed by more or 

 less distinct oblique growth-lines ; base with about 5 spiral separated 

 narrow ridges, often inconspicuous. Colour whitish, tinged with blue 

 on the body-whorl and yellowish or pinkish on the spire, all over 

 closely longitudinally marked with undulating purplish-red streaks, 

 often zigzag, or interrupted into spiral series of articulations. Epi- 

 dermis thin, shining, easily rubbed off. Spire elevated conic, sides 

 straight or slightly concave, more or less eroded, and showing the 

 iridescent green nacre at the tip. Protoconch conical, small, acute, 

 consisting of 2| convex smooth and pinkish-brown whorls. Whorls 



8 to 10, first very slowly, then rapidly increasing, straight or slightly 

 convex, the last distinctly angled at the periphery ; base flatly convex. 

 Suture well impressed, sometimes subcanaliculate on the lower whorls. 

 Aperture ovate-rhoniboidal, oblique, lined with iridescent green nacre 

 with red reflections. Outer lip thin, slightly sulcate within ; there 

 is often a broad opaque white callosity following a greenish edge 

 inside. Columetta sub vertical, generally straight "in the middle or 

 slightly projecting. Inner Up spreading as a broad white callus a little 

 beyond the columella and over the parietal wall. 



Diameter, 30 mm. ; height, 40 mm. 



Dentition unknown. 



Hob. From Cape Maria van Diemen to Cook Strait ; Preservation 

 Inlet ; Chatham Islands ; Snares ; Kermadec Islands. Brought to 

 England by Captain Cook. 



Var. biangulatus, Suter, 1908. Plate 33, figs. 6, 6a. 



Cantharidus opalus, Mart., var. biangulatus, Suter, P. Mai. S., viii, 22, figs. 

 in text. 



Differs from the species by the disproportional expansion of the 

 last whorl, beginning after the first quarter of the volution ; it rapidly 

 protuberates, getting broadly shouldered above, flat at the periphery, 

 and having a biangulate outline. There are about 8 whorls. The 

 suture along the swollen part of the last whorl is canaliculate. Aper- 

 ture subpentagonal ; base flatly convex. 



Diameter Maj., 27 mm. ; min., 23 mm. : height, 37 mm. 



Type in my collection. 



Hob. Cook Strait (Captain Bollons). 



