98 DEVONIAN FAUNA. 



1863. NucuLA LiNEATA, Semenoio and M'dller. Melauge Phys. et Chiin., vol. v, 



p. 678, pi. iv, fig. 11. 

 ? 1868. — PLiCATA, Dames. Zeitsch. Deutach. G-eol. G-esell., vol. xx, 



p. 502, pi. X, figs. 8 a, h. 



Description. — Shell small, subtriaiigular, oblique, very convex. Umbo large, 

 prominent, elevated, rounded, situated at or about the posterior third of the length, 

 and tending somewhat backward. Hinge-line convex, about half the length of 

 the shell, and ending abruptly at the sides, bearing a fossette and a few very 

 minute teeth under the umbo, about four large, high, perpendicular, parallel, pos- 

 terior lateral teeth, and about six still larger and loftier, perpendicular, parallel, 

 anterior lateral teeth. Anterior margin much produced, straight and oblique 

 above, and deeply convex round the anterior corner. Inferior margin long, 

 gently convex. Posterior margin broad, roundly convex. Surface with ten or 

 or twelve fine, sharp, elevated, very distant concentric ridges, between which 

 several very fine intermediate concentric strise are seen. Shell-structure very 

 thick. 



Size. — Height 5 mm., length 9 mm., depth of both valves 3 mm. 



Localities. — In the Barnstaple Athenseum is a specimen from Upcott, and 

 another from Briishford ; in the Museum of Practical Geology one from Saunton, 

 and another (which is very poor) from east of Ashford Inn ; in the Woodwardian 

 Museum three from west of Saunton Court ; and in my collection one from Upcott 

 Arch Quarry. Phillips records it from " Baggy Point." 



Bemarlcs. — From Phillips's description the species varied considerably in length, 

 size, and sculpture. The variation in contour is seen in our specimens, which 

 seem as a rule rather more transverse than his. Our specimens are, with one 

 exception, casts. It seems doubtful whether the possible crenulation of the striae 

 mentioned by Phillips is not simply due to fracture. In casts of the double shell 

 the impress of the lofty interlocked teeth leave a beautiful scalloped pattern, and 

 the margins protrude sharply at the ends of the hinge-line. 



2. Genus — Ctenodonta, Salter, 1851. 



(Ehlert,^ who discusses the question fully, points out that Tellinomya, Hall, 

 and Ctenodonta, Salter, having the same type species, are synonymous, and con- 

 siders the latter to be the valid name. 



He regards it as a genus distinguished from Palwoneilo, Hall, by its more 



1 1888, CEhlert, ' Bull. Soc. Geol. Er.,' ser. 3, vol. xvi, p. 653. 



