CTENODONTA. 99 



central and loftier umbones, its more largely rounded anterior side, the absence 

 of a postero-superior depression, and the subrostrated shape, which is after the 

 manner of Leda. On the other hand, Beushausen points out that the type species 

 of Ctenodonta had a depression behind ; and on the whole it is probable that 

 Palseoneilo, and (Beushausen adds) Koeuenia, should not be counted as more than 

 groups or sub-genera of Ctenodonta. 



1. Ctenodonta Newtonii, n, sp. Plate X, fig. 15. 



1895. CTENOUONTA, sp., Beusliausen. Abhandl. k. Preuss. Geol. Landes., n. s., 



pt. 17, p. 78, p]. V, fig. 23. 



Description. — Cast small, transversely ovate, sub-equilateral. Umbo small, 

 depressed, slightly recurved, and situated somewhat in front of the centre. 

 Hinge-line gently bent, about two-thirds of the length, and bearing five or six very 

 minute perpendicular teeth, uninterrupted by a f ossette, under the umbo, five or six 

 large, parallel, perpendicular anterior teeth, and about twelve large, lofty, parallel, 

 perpendicular posterior teeth. Posterior side broad, much produced, with a deeply 

 convex margin. Inferior margin very long, gently convex. Anterior side broader, 

 with a more evenly convex margin. Surface covered by very numerous, regular, 

 minute, distant, concentric strias. Contour of back gently convex, steeper in front 

 than behind. 



Size. — Height 9 mm., length 12 mm., depth of the cast of one valve 2 mm. 



Localities. — In the Barnstaple Museum are two specimens from Fremington ; 

 and in my Collection two from Frankmarsh, and a fragment from Ironpost. 



Remarks. — These shells seem to agree in shape and ornament with the imper- 

 fect valve which Beushausen figures from the Upper Coblenzian of Sechelden. 



Though our specimens are chiefly casts, evidence of the nature of the ornament 

 is obtainable. 



The species is named after R. B. Newton, F.G.S., whom I have to thank for 

 kind assistance. 



Affinities. — Nucula fornicata, Goldfuss,^ is similarly marked, but is larger and 

 deeper, and has a loftier and more lateral umbo and a fossette. 



N. lineata, Phillips, is more convex and oblique, and has a much coarser 

 ornamentation. 



It appears to be sometimes approached by the very variable N. domina^ 

 Barrande,^ which seems similarly ornamented. 



1 1834-40, Goldfuss, Petref. Germ., vol. ii, p. 151, pi. cxxiv, figs. 5 a — c. 

 " 1881, Barrande, ' Sjst. Sil. Bolieme,' vol. vi, pi. cclxxiv, fig. 1, s-ic, Et. D. 



