PTERIA. 07 



ventral margins being- smaller, and by the shorter postero-ventral margin. It also 

 resembles P. (Pseudoptera) ignabergensis (Lundgren), 1 from the Senonian of 

 Ignaberga. 



P. (Pseudoptera) haldonensis is distinguished from the young of /'. (Pseudoptera) 

 anomala (see above) by its sharp carina; by the part of the valve behind the carina, 

 and the posterior wing, being smooth; also by the strong and more widely sepa- 

 rated ribs in front of the carina. 



Types. — In the British Museum and the Sedgwick Museum. 



Distribution. — Upper Greensand (zone of Pecten asper) of Haldon. 



Pteeia (Psetjdopteka) gaultina, sp. nov. Plate IX, figs. 11 a, b, 12 a, b. 



Description. — Shell small, very oblique. Umbo acute, near the anterior 

 extremity. Apical angle 26° to 32°. 



Left valve moderately convex, with the median triangular part raised but 

 flattened ; in front of this the valve bends sharply to the anterior margin ; behind, 

 it bends rather sharply to join the posterior ear, which is distinctly demarcated. 

 Anterior ear small. Posterior ear moderately large, united to the greater part of 

 the postero-dorsal margin of the valve ; its posterior margin concave. 



A few narrow, well-defined radial ribs occur on the anterior part of the raised 

 triangular portion and just in front of it. In some cases less distinct ribs with 

 spiny projections are present on the whole of the triangular part of the valve. 

 Growth-ridges are often well-marked, and are continued on to the posterior ear. 



Measurements ■. 



Hinge-line . . . . .11 mm. 



Height (oblique) . . . . 21 „ 



Black Von. 



Affinities. — This species is distinguished from Vteria (Pseud opt cm) haldonensis 

 (see above) by (1) the greater obliquity of the shell, (2) the smaller apical angle, 

 (3) the absence of the sharp carina, (4) the distinctly limited posterior ear. 



Types. — In the Museum of Practical Geology (No. 10,780) and the Sedgwick 

 Museum. 



Distribution. — Gault of Black Ven. 



Pteiua (Pseudoptera) ciekulescens (Nilsson), 1827. Plate IX, figs. 13-10, 17 a, b, 



18, 19./,//. 



1H-J7. Avicula C(Erxjlescens, S. Nilsson. Petrif. Sueeana, p. 18. pi. iii, fig. li» 

 ? 183G. — A. Goldfuss. Petref. Genu., vol. ii, p. 132, pl.cxviii, 



fig. 6. 

 1 ' Mollusk. i Mammilatus och Mncronata Zouerua i Nordostra Skane ' (1894), p. 44, pi. i, fig. 2. 



