MONODONTA. 97 



Australasian forms is the band of nacre extending across the ]iarietal 



wall, connecting the terminations of the peristome. The species are 



dark colored, like nearly all Trochida? of the Avest coast of the 



Americas. This melanism is i)rol)ably a protective adaptation, for 



the prevailing hne of the rocks of these shores is very dai'k. 



M. NIGERRIMA (Gmel.) Philippi. PL 23, figs. 77, 78 ; pi. 20, tig. 



18. 



Shell imperforate, depressed globose, solid, slate-colored or black, 

 sometimes (especially if rubbed) reddish or brownish ; sj)ire short, 

 conic, apex acute, usually reddish ; sutures linear ; whorls 5, slightly 

 convex, rapidly increasing, spirally obsoletely striate, the last whorl 

 usually depressed or subconcave below tlie suture; base rounded, 

 eroded and iridescent in front of the aperture ; aperture huge, 

 oblique iridescent ; the outer lip rather thin, not black-margined 

 within ; but bordered by a brilliantly iridescent band ; columella 

 concave, obsoletely subdentate below, very broad and flattened or 

 excavated on the face, composed principally of an opaque white 

 layer which also lines the base but does not extend to the edge of the 

 lip. Alt. 15-26, diam. 17-24 mill 



Coast of Chili. 



Turbo nigerrimua Gmel., Syd. Nat., xiii, p. 3597 (not Trochus 

 nigerrimus Gmel., a species of Chlorostoma). — Trochus )iigerrinms 

 Philippi, Conchyl. Cab., p. 149, t. 24, f 14. — Trochus araucanus 

 D'Orbigny, Voy. dans VAmcr. merid., p. 410, t. 55, £ 5-8 (1846). — 

 Gould, U. S. E.vpL Exped., 1. 13, f 215. — Fischer, Coq. Viv. (Turbo), 

 p. 110, t. 29, f 2. — Turbo Quoyi Kiener, Spec, et Icon. (Turbo), t. 

 29, f 2. (Not Trochus Quoyi Phil.) 



The above description is drawn from specimens brought by Dr. 

 Ruschenberger from Valparaiso, the original locality. The sur- 

 face is either black and shining, or presents a corroded appearance. 

 The spiral sculpture is obsolete on the last whorl, in large specimens, 

 but traces of it may usually be seen upon the base. I do not think 

 this species has been found except upon the S. American coast, 

 although Professor Hutton and others quote it from New Zealand. 

 The dentition of the New Zealand form is quite different from that 

 of the real S. American M. nigerrima. While there may be some 

 slight doubt about the identity of this species with the T. nigerrimus 

 of Gmelin, it is undoubtedly the shell described under that name by 

 Philippi. Turbo Quoyi Kn. and T. araucanus d'Orb., are certainly 

 the same ; and it is equally certain that the Diloma nigerrima of 



