Onithochiton.] AMPHINEURA. 49 



3. Onithochiton undulatus, Quoy and Gaimard, 1835. Plate 2, 

 fig. 24 ; Plate 5, fig. 5. 



Chiton undulatus, Q. & G., Voy. Astrol., iii, 393, pi. 75, f. 19-24. Onitho- 

 chiton undulatus. Q. & G., Man. Conch., xiv, 245, pi. 55, f. 1416; 

 P. Mai. S.. ii. 199. Tonicia lineolata, Frembly : Button, M.N.Z.M., 

 114. not of Frembly. 



Shell oblong, moderately elevated, the dorsal angle rounded, side 

 slopes nearly straight, colour very variable, mostly olive with con- 

 centric brown lines. Anterior valve with obsolete radiating riblets, 

 and rays of eyes, the eye-rays variable in number, width, and degree 

 of coalescence, the. individual eyes being very mutable in number 

 and position. Intermediate valves beaked, central areas smooth and 

 polished, lateral areas but little raised, and either smooth or sculp- 

 tured with 4 or 5 low more or less obsolete beaded radiating riblets, 

 and showing under a lens a band of eye-dots near the front margin. 

 Posterior valve very shortly subtriangular, the distance from sinus 

 to mucro being but little more than one-third the width of the valve's 

 tegmentum. Girdle yellowish-white, with very minute brown dots. 

 Colour extremely variable ; various shades of green, yellowish on 

 the ridge, or buff, flesh-colour, light blue, &c. ; always with concentric 

 darker lines, more distinct on the sides ; sometimes the first 2 valves 

 of a light pink, the others dark olive on the sides, yellowish-white in 

 the middle, &c. Interior white or light blue, chestnut under the beak 

 of each valve ; anterior valve with 8 slits, intermediate valves with 1 

 slit, on each side ; teeth obtuse, closely and sharply pectinated outside 

 and on the summits ; posterior valve with a narrow convex ridge ; 

 sinus deep, angular, finely denticulate ; sutural laminae broad, higher 

 toward the sinus. 



Length, 25 mm. ; breadth, 16 mm. : a large specimen, 30 mm. 

 by 19 mm. Divergence, 110. 



Type in Mus. Hist. Nat., Paris. 



Hob. Throughout New Zealand and the Chatham Islands ; under 

 stones between tide-marks, and in kelp-roots. 



Var. subantarcticus, Suter, 1907. 



Onithochiton undulatus, Q. & G., var. subantarcticus, Suter. TNZI 

 xxxix, 1906 (1907), 268. 



This colour variety is usually of uniform chocolate or purplish- 

 brown colour, sometimes with white patches on the ridge, or, though 

 very rarely, the second, the fifth, and sixth valves partly or entirelv 

 white with, concentric lines of brown. One specimen I disarticulated 

 had only 6 slits in the anterior valve, but others have the normal 

 8 slits. 



Type, from the Auckland Islands, in my collection. 



Hob Auckland and Campbell Islands, Cook Strait, and New 

 Brighton, but rare. 



