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SUPPLEMENT TO THE BRITISH 



straight. Dorsal valve convex, smooth, inflated at the umbo, interior with a plain 

 border, within which is a raised serrated margin, from which arises a longitudinal medial 

 lanceolate septum occupying two-thirds the length of the shell, the muscular depression 

 is smooth. This species is related to T. rmticum, T. granulosum, and T. triangulare, 

 but presents a combination of characters which distinguishes it from them. 

 "Locality. — Brocastle. Zone of Am. angulatus" (Tate). 



Not having had the advantage of being able to examine specimens of this shell, I 

 have reproduced Mr. Tate's description. It is not recorded as having been found higher 

 up than the Lower Lias. 



55. Thecidium Deslongchampsii, Dav. Appendix to vol. i, p. 14, PI. a, fig. 6, 6 a. 

 Nothing new. Middle Lias (zone of Am. margaritatus). 



56. Thecidium duplicatum, Moore. Dav., Supplementary Appendix to vol. i, p. 30. 



Sup. PI. XII, figs. 15 to 20. 



Thecideum duplicatum, Moore. Proc. of the Somersetshire Archaeological and 



Nat. Hist. Soc, pi. ii, figs. 7—12, 1854. 



Mr. Moore observes, that the interior of the dorsal valve of this species is very 

 variable, that in some instances the internal ridges are formed by widely-separated gra- 

 nulations, that in others they are continuous. The ridges are spinose. 



I have seen all the original specimens from which Mr. Moore's figures have been 

 taken, and can consequently answer for their accuracy. The shell slightly exceeds one 

 line in length by something less than two in width. It occurs in the Inferior Oolite 

 of Dundry. 



57. Thecidium serratum, Moore. Dav., Supplementary Appendix to vol. i, p. 30, 



and Sup., PI. XII, figs. 10 to 14. 



Thecidium serratum, Moore. Proc. of the Somersetshire Archaeological and Nat. 

 Hist. Soc, vol. for 1854, p. 119, pi. iii. figs. 1—6. 



As this species was very briefly described in the Supplementary Appendix to the first 



