102 DEVONIAN FAUNA. 



Beusbausen has described several species of Palseoneilo from the Spirifer-sand- 

 stein of the Oberharz, but being for the most part casts they are not easy to 

 compare ; P. brevis, Beushausen/ looks exceedingly like our specimens. 



Ctenodonta unioniforniis, Sandberger,^ as given by Beushausen,^ seems to 

 approach nearly, but it is larger and more unevenly ornamented, while Gt. gibbosa, 

 Goldfuss,* not Sow., sp., as given by him, seems also to be a shorter shell. I 

 should not, however, be surprised if they both prove to be varieties of the present 

 species. 



3. Ctenodonta (Pal^oneilo) antiqua, Sowerby, sp. Plate XIII, fig. 5. 



1840. Ptjllastea aktiqtja, Sowerby. Geol. Trans., ser. 2, vol. v, pt. 3, pi. liii, 



fig. 28. 

 1855, Ntjctjla pullastuifobmis, M'Coy. Brit. Pal. Foss., p. 397. 

 1893. Ctenodonta antiqua, Collins. Trans. Roy. Geol. Soc. Cornw.,' vol. xi, 



p. 36. 

 ? 1895. — DALEiDENSis, JBews^awsew. Abhandl. k. Preuss. Geo]. Landes., 



n. s., pt. 17, p. 85, pi. vi, fig. 6. 



Description. — Shell rather small, transversely ovate, moderately convex. 

 Umbo small, proximate, rather prominent, incurved, tending forwards, and situated 

 at the anterior third of the length. Hinge-margin long, straight posteriorly. 

 Anterior margin deeply convex or subangular. Inferior margin long, gently 

 and evenly convex. Posterior margin convex, rather broad. Contour gently 

 convex, with a very slight and narrow posterior slope. Surface with about thirty 

 distant, regular, elevated concentric lines. 



Size. — Height 12 mm., length 19 mm. 



Localities. — Six specimens from Marwood are in the Barnstaple Athenaeum; 

 one from Marwood is in the Museum of Practical Geology; and Sowerby's type 

 from Marwood is in the Woodwardian Museum. 



Remarks. — This species seems to characterise the Sloly Beds, and to be variable 

 in shape, its transverseness decreasing with age. 



Its name was changed by M'Coy on placing it in the genus Nucula, but as it 

 belongs to Ctenodonta or Palseoneilo, it may resume its original name. The pos- 

 terior depression is very narrow and indistinct, perhaps even more so than 



1 1884, Beushausen, ' Abhandl. Geol. Specialk. Preuss.,' Band vi, pt. 1, p. 79, pi. iii, fig. 12. 



2 1853, Sandberger, ' Verst. Khein. Nassau,' p. 277, pi. xxix, fig. 1. 



3 1895, Beushausen, * Abhandl. k. Preuss. Geol. Laudes.,' n. s., pt. 17, p. 84, pi. vi, figs. 10 — 15. 



4 1834-40, Goldfuss, ' Petref. Germ.,' vol. ii, p. 278, pi. clix, fig. 10. 



^ 1895, Beushausen, ' Abhandl. k. Preuss. Geol. Landes.,' n. s., pt. 17, p. 83, pi. vi, fig. 16. 



