82 DEVONIAN FAUNA. 



3. Edmondia ? Hamlingii, n. sp. Plate XI, fig. 3. 



Description. — Shell large, transverse, sub-equilateral, very convex. Umbo 

 large, rounded, incurved, direct, extending above the hinge-line, and situated a 

 little in front of the centre. Anterior and posterior margins evenly and deeply 

 convex, the latter being the broader. Inferior margin long, gently convex. 

 Hinge-line shorter than the length of shell. Contour of back evenly convex. 

 Surface covered with very numerous, fine, irregular growth-lines. 



Size. — Height 23 mm., length 32 mm., depth of valve about 10 mm. 



Locality. — One specimen is in Mr. Hamling's Collection, in a pebble from 

 the beach at Saunton Point. 



BemarJcs. — The umbo and hinge of this fine specimen are obscured by the hard 

 gritty matrix, and it is impossible to decide its exact generic position. It appears 

 far removed from any of the other species of our beds, being marked by its 

 remarkably regular, convex, oval form, and the central position of its umbo. As 

 it bears most general resemblance to some species of Edmondia described by 

 de Koninck, it seems best to refer it provisionally to that genus. In the same 

 pebble, specimens of Strophalosia productoides, Athyris concentrica, and Ortliis 

 interlineata occur. 



Affinities. — It seems to have a larger umbo than E. orhitosa, de Ryckholt^ 

 and E. prselata, de Roninck.^ 



4. Genus — Sphenotds, Hall, 1885. 



Shell equivalve, very unequilateral, elongate, sub-trapezoidal. Anterior end 

 short. Posterior end obliquely truncate. Beaks sub-anterior. Hinge-line long, 

 nearly straight. Umbonal ridge defined. Postero-superior slope marked 

 characteristically with a median ridge. Back with a broad median depression, 

 sometimes producing a constriction in the margin. Surface concentrically striated. 

 Hinge narrow, with two short narrow central teeth in right valve, and two extremely 

 slender lateral teeth. Ligamental groove slender, external. Anterior muscle-scar 

 strong, marginal. Posterior scar shallow. Pallial line simple. 



The above description is condensed from Hall, who states that the genus 

 differs from Sanguinolites and Allorisma by its umbonal and post-cardinal ridges, 

 its trapezoidal shape, its central cincture, and the character of the hinge. 



Judging by the external characters, the following species appear referable to it. 



1 1885, de Koninck, 'Ann. Mus. Eoj. H. "N". Belg.,' vol. xi, p. 36, pi. xiii, figs. 18-26. 



2 Ibid., p. 36, pi. xiii, figs. 26, 27. 



