106 DEVONIAN FAUNA. 



its surface is undescribed. It may be distinguished by having a loftier umbo and 

 blunter anterior side, and perhaps by its hinge-line. 



Ct. hercynica, Beus.,^ is a similarly doubtful analogue. 



Suh-gemis — Koenenia, Beushausen, 1884. 



Beushausen separated this as a genus on account of its bent hinge-line and the 

 absence of a marginal area to it, giving Nucula Jasii, Eomer, as the type species'; 

 but in his later work (1895) he sinks it as a group of Gtenodonta. 



6. Ctenodonta (Koenenia) cf. obsoleta, Goldfuss, sp. Plate XII, fig. 10. 



Description. — Shell of moderate size, very transverse, very convex. Umbo 

 large, flattened, incurved, and probably proximate, situated at or about the anterior 

 third, and tending forward. Inferior margin long, nearly straight. Lateral 

 margins apparently narrow and very deeply convex. Hinge-line gently arched, 

 nearly as long as the shell, and very wide, imperfectly seen but bearing four or 

 five very large, massive, vertical teeth at its extremities, and probably many 

 others between them, which appear to become very minute near the umbo. 

 Contour deeply and regularly convex, being steepest on the anterior side. Shell- 

 structure very massive. Surface unknown. No clavicular process. 



Size. — A defective valve measures about 17 mm. high, 30 mm. wide, and 

 7 mm. deep. 



Localities. — Two casts from Braunton and one from Baggy Point are in the 

 Museum of Practical Geology, and another from Frankmarsh is in my Collection. 



Bemarhs. — These fragmentary casts show no signs of any clavicular process. 

 They seem remarkable for the great size of the hinge and of the teeth ; the latter 

 having an appearance of being joined by slight transverse bars, which may, 

 however, be due to accident. They certainly seem distinct from any accom- 

 panying species ; but unfortunately the most characteristic specimens are too 

 imperfect for figuring. 



They bear resemblance to Nucula obsoleta^ Goldfuss,^ and to Ciicullsea Jasii, 

 F. A. Romer,^ but in neither case is it easy to form an accurate idea of the exact 

 shape of these German shells. Beushausen,* indeed, describes a shell more fully 



1 1884, Beushausen, ' Abliandl. Gaol. Specialk. Preuss.,' Band vi, pt. 1, p. 76, pi. iii, fig. 12. 



2 18.34-40, Goldfuss, ' Petref. Germ.,' vol. ii, p. 151, pi. cxxiv, fig. 6. 



3 1843, F. A. Eomer, ' Verst. Harzgeb.,' p. 24, pi. vi, fig. 15. 



* 1884, Beushausen, ' Abhandl. Geol. Specialk. Preuss.,' Band vi, pt. 1, p. 73, pi. iii, figs. G, 7. 



