68 DEVON [AN FAUNA. 



the moutli, the strong keel on the back of the expansion, and the much smaller 

 size of the spire. Whether in these particulars it agrees with the English shell 

 I am not sure. 



It may be noted that figures given by Hall ^ of his B. pelops show a similar 

 keel in the cast, but a regular small round keel in the perfect shell. From our 

 shells they differ in not having the mouth so extremely expanded. 



3. Genus or Sub-genus — Teopidodiscus, MeeJc, 1866. 



This genus or sub-genus contains shells akin to B. trilobatus, Sow., which are 

 very flat, with very wide and open umbilici, and with a rounded convexity bounded 

 by two concavities on the back of the whorl, but without any definite sinus-band. 



De Koninck proposed to replace Meek's name by Tropidocydus, because Stein 

 in 1850 had used the name Tropidiscus. As Meek had himself emended the latter 

 name, which he had used at first, there appears to be no reason for a further 

 change. 



Fischer^ regards Meek's name as a synonym of Cyrtolites, Conrad, 1838. 



1. Teopidodiscus trilobatus, Sowerhy ? var. bisuloatus, F. A. Eomer. Plate VIII, 



figs. 6, 6 a. 



? 1839. Belleeophon teiloeattjs, Sowerhy. In Murchison, Sil. Syst., p. 604<, pi. iii, 



fig. 16. 



1840. — — de Ferussac and d'Orhigny. Hist. Nat. Ceph., 



p. 209, (Bellerophon) pi. vii, 

 figs. 34—37, and pi. viii, fig. 13. 



1841. — — Phillips. Pal. Foss., p. 107, pi. xl, 



figs. 200 a—e. 

 1843. — BisTJLCATTJS, F. A. Romer. Verst. Harzgeb., p. 32, pi. ix, 



figs. 1 a, b. 

 ? 1843. — TEiLOBATus, F. A. Bomer. Ibid., p. 32, pi. xii, fig. 39. 



1853. — — var. ttpus, Sandlerger. Verst. Ehein. Nassau, 



p. 177, pi. xxii, figs. 2, 2a. 

 1855. — BisuLCATUS, WCoy. Brit. Pal. Foss., p. 400. 



1877. — TRILOBATUS, (EUert. Bull. Soc. Geol. Fr., ser. 3, vol. v, 



p. 580. 



J 1879, Hall, ' Pal. N. Y.,' vol. v, pt. 2, p. 95, pi. xxii, figs. 7—13. 

 2 1887, Fischer, ' Manuel Conchy!.,' p. 854. 



