CTENODONTA. 105 



arched, bearing, at least on the posterior side, very numerous, small, short, 

 parallel, oblique teeth. Posterior hinge-margin long, nearly straight, slightly 

 oblique. Posterior margin narrow, and so deeply convex as to be nearly 

 subangular. Inferior margin very long and gently convex. Contour of back 

 moderately and evenly convex. Surface covered by numerous minute, irregular, 

 parallel, sharpish, concentric strige, one or two of which are definitely larger than 

 the rest. 



Size. — Height 10 mm., length 27 mm., depth of one valve about 3'5 mm. 



Locality. — A fine specimen and its mould from Sloly are in the Barnstaple 

 Athenaeum. A cast from Barnstaple in the Museum of Practical Geology may 

 belong to the same species. 



Bemarlcs. — As its interior is not certainly known its genus cannot be 

 decided. The cast from Baggy differs so much that it is very doubtful if it is 

 identical. The species appears to be well characterised, although there may be 

 a little uncertainty about its exact shape, owing to the great amount of squeezing 

 which the beds have evidently undergone. It occurs in the Lingula squamiformis 

 beds. 



Affinities. — Leda perdentata, Barrande, which belongs to the genus NiicuUtes, 

 may possibly prove to be the same species. 



The vaguely figured and described Nucida latissima of Phillips, seems broader 

 behind, and is more likely to represent the shell described below than the 

 present species. 



From Ctenodonta lirata and Ct. antiqua it differs by its much greater length, 

 and by its much finer and more irregular ornament, as it shows little or no signs 

 of the lofty regular concentric bars which cover the surface of those shells. 



Cucullella tumida, Sandb.,^ which has somewhat the same dimensions, differs 

 in being still longer and more trigonal. 



Nucula solenoides, Goldfuss,^ has a concave hinge-line, and N.prisca, Goldfuss,^ 

 appears to be more trigonal. 



Palseoneilo attenuata, Hall,* has a median constriction on the back ; and 

 P. sidcatina, Hall, though closely resembling it, seems to have a loftier umbo and 

 more lamellar ornament. 



Sanguinolaria elliptica, F. A. Eomer,^ not Phillips,^ approaches in shape, but 



' 1853, Sandberger, ' Verst. Rhein. Nassau,' p. 277, pi. xxix, figs. 6, 6 a. 

 2 1834-40, Goldfuss, ' Petref. Germ.,' vol. ii, p. 151, pi. cxxiv, fig. 9. 

 * Ibid., p. 151, pi. cxxiv, fig. 7. 

 ^ 1885, Hall, ' Pal. N. Y.,' vol. v, pt. 1, No. 2, p. 346, pi. 1, figs. 34—39. 



5 1843, P. A. Eomer, ' Verst. Harzgeb.,' p. 26, pi. vi, fig. 27 ; and 1884, Beushausen, ' Abhandl. 

 Geol. Specialk. Preuss.,' Band vi, pt. 1, p. 73, pi. iv, fig. 24. 



6 1841, Phillips, ' Pal. Poss.,' p. 34, pi. xvii, fig. 53. 







