24 AMPHINEURA. [Polyplacophora. 



behind. This was, no doubt, produced when the specimen was dried ; 

 in fresh examples I never observed a posterior sinus. The bundles 

 of about 3 large horn-like hairs at the sutures, mentioned by Car- 

 penter, are not shown in the photograph of the type, and are certainly 

 not a regular feature. This character, now proved to be incorrect, 

 has always prevented me from uniting the two species. 



Sect. 3. FREMBLYA, H. Adams, 1866. 

 FnnMya, H. Ad.. P.Z.S., 1866, 445. Type : F. egregia, H. Ad. 



Shell and girdle like Plaxiphora, except that the former is short 

 and broad, the tail valve very much reduced in size, strongly arched 

 upward in the middle behind. Slits in intermediate valves posteriorly 

 situated. Girdle having more or less obvious sutural pores. 



8. Plaxiphora ovata, Hutton, 1872. Plate 2, fig. 8 ; Plate 3, fig. 15. 



Acanthochcetes ovatus, Hutt., T.N.Z.I., iv, 182. Plaxiphora ovata, Hutt., 

 Man. Conch. (1). xiv, 332, pi. 54, f. 34-40. 



Shell short-oval, very wide in the middle, very rapidly narrowing 

 toward the ends ; moderately elevated, the dorsal ridge carinated, 

 side slopes slightly convex. Surface lustreless, sculpture in herring- 

 bone pattern. Colour buff. Anterior valve small, its width about 

 that of one side slope of the fourth valve, its apex elevated and slightly 

 recurved ; surface having 8 strong ribs, besides those at the sutural 

 margins, the anterior rib strongest and wider apart ; ribs nodose, 

 intervals obliquely corrugated. Median valves broadly V-shaped, the 

 apices of the valves elevated and acute. Lateral areas narrow, a 

 little elevated, the diagonal rib sculptured with a series of closely 

 superimposed Vs, their apices directed toward the beak of the valve, 

 one limb of each V directed outward, curving, and forming the sculp- 

 ture of the pleura, the other limb forming an oblique corrugation of 

 the lateral area. Sutural margin of each lateral area oblique, coarsely 

 granose. Central areas having a nearly smooth band along the dorsal 

 ridge, and numerous slightly curving and diverging riblets on each 

 side. Posterior valve small, forming an extremely narrow crescent, 

 strongly curved upward at the acute posterior mucro, the front 

 (" central ") area narrow, concave ; viewed from behind, it presents 

 the appearance of a wide inverted V. Girdle rather narrow, yellowish, 

 bearing a pore-tuft of hyaline white bristles at each suture and a 

 fringe of bristles at the edge. Colour buff along the ridge, pale olive- 

 green on the side slopes, with a small curved dark spot or two on 

 each valve. Interior bluish-white ; anterior valve having 8 slits, 

 median valves 1 slit ; posterior valve having a keel-like insertion 

 plate without slits on each side, and a broad sinus in the middle behind ; 

 sinus exceedingly broad, rounded, the sutural plates widely separated ; 

 insertion plates long, having the slit near the posterior edge of the 

 plate. (Pilsbry.) 



