92 PROCEEDrJSTGS OF THE MALACOLOGICAL SOCIETY. 



18. AcANTHocHiTEs (NoTOPLAx) GLTPTus, n.sp. PI. VI, Figs. 5, 5a. 



Shell rather elongate. Exposed portions of valves rather large in 

 proportion. Valves elevated and sharply keeled ; dorsal area nearly- 

 white ; other areas of a salmon- pink colour, mottled with greyish, in 

 varying pattern, but darkest near to the dorsal area. Girdle olive- 

 brown ; the tufts of a lighter colour. Intermediate valves convex 

 behind and slightly concave in front. Dorsal area wedge-shaped, 

 moderately largo, smooth to the naked eye, but showing indistinct 

 traces of sculpture under a lens. Lateral areas small, smooth, very 

 slightly elevated, and separated from the pleural areas by an indis- 

 tinct diagonal. Pleural areas smooth, except for four incised lines 

 on each side, which, if produced over the lateral areas, would meet 

 at about the beaks of the valves. Anterior valve smooth, except 

 for five very flattened ribs, corresponding to the slits in the valve. 

 Posterior valve sculptured before the mucro, which is at about the 

 posterior third, as the intermediate valves ; behind the mucro it is 

 smooth, save for traces of radiating ribs. Girdle with short, obscure 

 spicules, and having 16 (?) tufts. Interior of valves whitish, with 

 traces of green staining. Valve- slits : anterior 5, median 1-1, 

 posterior 6. Two of the slits in the posterior valve may be caused 

 by the splitting of a median one. Length about 22 mm., breadth 

 about 7 mm. 



This shell is remarkable for the entire absence of well-marked 

 sculpture, except the striking incised lines. There appears to be no 

 other known species approaching it. 



19. AcANTHOcniTES (NoTOPLAx) "WiLSONi, n.sp. PI. VI, Pigs. 2, 2a. 



Shell moderately elongated, the visible portions of the valves occu- 

 pying about one-third the total width. Valves elevated, moderately 

 keeled ; the ridge being marked with bands of reddish and salmon- 

 pink ; the lateral areas of a dark red ; the pleural areas being marked 

 with a red and white. Girdle olivaceous, densely clothed with spicules, 

 but showing no visible tufts. Intermediate valves convex behind and 

 concave in front, with well-marked beaks. Dorsal area of an elon- 

 gate wedge-shape, well separated from the side areas, smooth to the 

 naked eye, but marked under a lens with longitudinal and transverse 

 striae. Latero-pleural areas having no trace of a diagonal rib, sculp- 

 tured all over with well-marked flattened tubercles. The anterior 

 valve shows the latter sculpture all over. The posterior valve has 

 an elevated and rather pointed mucro at about the posterior third. 

 Interior of valves whitish, becoming stained with red under the 

 jugal area. Valve-slits: anterior 5, median 1-1, posterior 6. Length 

 about 25 mm., breadth about 10 mm. 



The following valuable note, by Mr. Pilsbry, will give a better idea 

 of it than any words of my own. " It differs from A. MaWietosi 

 in having the entire latero-pleural tracts granose-lirate, while only 

 the lateral areas are grauose in the otlier ; the tegmentum, especially, 

 of the head-valve is smaller; the tail-valve approaches that of the 

 typical Notoi)lax in form, and the girdle is densely clothed, though 



