ACANTHOCHITES-LOBOPLAX. 39 



Carpenter considered " Phacellopleura " (porphyretica, violacea) a 

 genus of Ischnoid Acanthopleuroids, but he describes A. costatus in 

 Acanthochites. I cannot give the group generic rank because 

 Notoplax connects it with Acanthochites. 



A. viOLACEUS Quoy & Gaimard. PI. 3, figs. 67-73. 



Elongated, rather depressed ; the valves all of the same width 

 except the last which is narrower. Color typically a rich, dark 

 purple-brown, the girdle darker, varying to violet with a buff' tri- 

 angle at the ridge of each valve enclosing a purple stripe or series of 

 spots ; or sometimes ashy whitish, faintly tinged with purple along 

 the middle. 



Intermediate valves (fig. 68) having the tegmentum trilobate, much 

 narrowed in front by the encroachment of the girdle at the sutures ; 

 beaks small. Dorsal areas triangular, wide in front, convex, polished, 

 sculptured with elongated punctures along the sides. Latero-pleural 

 areas sculptured with pebble-like low granules, coarser and often con- 

 fiuent along a diagonal line from the beak to the outer-anterior angle. 

 Anterior valve (fig. 67) having b prominently projecting lobes, corre- 

 sponding to radiating rounded ribs ; the scale-granules of the sur- 

 face coalescing more or less on these ribs. Posterior valve (figs. 69, 

 70) having the tegmentum slightly broader than long, the mucro 

 low, slightly post-median. 



Interior light blue-green, fading on the sutural-laminse. Sinus 

 deep, angular. Anterior valve with 5, median valves 1 slit. Poste- 

 rior valve having a deep Mopaloid slit on each side, and about 4 

 shallower slits between, -the teeth vertical, deeply grooved outside and 

 lobed at the edge. 



Girdle wide, leathery, smooth except for a minute pore at each suture 

 and 4 around the head valve ; each pore bearing a small tuft of 

 white spicules, usually broken short. 



Length 50, breadth 23 mill.; divergence of tegmentum 140°. 



Length 35, breadth 18 mill. ; divergence of tegmentum 130°. 



Length — breadth — (specimen rolled) ; divergence of tegmen- 

 tum 150°. 



New Zealand at Tasman Bay (Q. & G.) ; Auckland (Hutton, 

 Wright); Dunedin; Cook Strait {^witon.) 



Chiton violaceus Q. & G., Voy. de I'Astrol. iii, p. 403, t. 73, f 15- 

 20.— Gould., U. S. Expl. Exped Moll., p. 331, f 420. Not Chiton 

 violaceus Reeve, Conch. Icou., f. 41. — Chiton porphyreticus Reeve, 



