18 AMPHINEURA. [Polyplacophora. 



1. Plaxiphora aucklandica, Suter, 1909. Plate 3, fig. 10. 



Plaxiphora aitcklnndicn, Suter. Subantarct. Islds. N.Zeal., i. 1909. 2. 

 pi. 1. f. 1. 



Shell small, elongately oval, depressed, valves very fragile, dorsal 

 ridge subangular ; colour light brown, jugal tract whitish, white 

 dashes on the sides ; girdle wide, black, with sutural tufts of very 

 long bristles. Anterior valve short and broad, flattish, with 8 granu- 

 lated radial ribs. Intermediate valves wide, depressed, the jugum 

 smooth, roundly angled ; pleural tracts smooth, with very fine growth- 

 lines ; lateral areas not raised, with 2 narrow granulated ribs, the 

 interspaces smooth. Posterior valve smooth, small, the mucro pos- 

 terior, the hind slope nearly straight. Girdle broad, with very pro- 

 minent sutural tufts formed by 3 to 4 very long light-brown bristles ; 

 5 tufts round the anterior and a few round the posterior valve ; a 

 second series of tufts with shorter bristles near the margin, which is 

 beset with short brownish hairs ; remainder of the girdle quite naked, 

 smooth. Colour of the valves light brown, intermediate and tail 

 valves usually with a dorsal triangular white area with a longitudinal 

 brown median line ; 1 or 2 white elongated spots are mostly present 

 on the pleural, rarely on the lateral, areas ; girdle black. 



Length, about 15 mm. Divergence, 105. 



Type in the Canterbury Museum, Christchurch. 



Hab. Musgrave Harbour, Auckland Islands (Edgar R. Waite). 



Remark. The valves are so exceedingly brittle that it was impos- 

 sible to disarticulate the specimen without completely destroying it. 



2. Plaxiphora biramosa, Quoy and Gaimard, 1835. Plate 3, fig. 4 ; 



Plate 2, fig. 11. 



Chiton biramosus, Q. & G., Voy. Astrol.. iii, 378. pi. 74. f. 12-16. Plaxi- 

 phora biramosa, Q. & G., Man. Conch. (1). xiv. 319. pi. 68, f. 51-54: P. 

 Mai. S-, ii. 188. P. setiger. King : Wissel. Zool. Jahrb.. Syst.. xx. 603. 

 pi. 22, f. 16-18. not of King. 



Shell ovoid, elongated, flattened, valves very transverse, girdle 

 red-brown, with bifurcating bristles at the sutures. Anterior valve 

 with 8 radiate ribs, cut into nodules by zigzagging concentric shallow 

 grooves. Intermediate valves much depressed, with the jugum keeled ; 

 pleural areas densely longitudinally wrinkled, the wrinkles coarse in 

 front of the lateral areas, finer in front, oblique on the jugum ; lateral 

 areas concentrically wrinkled, 2 strongly nodulous ribs one in front, 

 the other at the suture. Posterior valve small, slightly concave, trans- 

 versely striated ; an elevated ridge runs to the terminal mucro, which 

 forms a transverse ridge. Girdle vivid red, having 2 spaced series 

 of rough, sparse, and bifurcating hairs, the inner series contiguous to 

 the valves, the other near the periphery of the girdle, which is also 

 hairy. Besides the sutural pores there are 5 in front and 2 behind. 

 The girdle with a deep posterior slit, its depth, however, being variable. 

 Colour mostly green, with longitudinal red-brown flamules on the 



