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SUPPLEMENT TO THE BRITISH 



generally much more acuminated than in L. Beanii, and its outline more subovate. It 

 occurs throughout the Middle Lias, and assumes very often a black appearance. It was- 

 found abundantly, and of large dimensions, in the Marlstone or Middle Lias, at Mickleton 

 Tunnel and Bathford, near Bath. Also in the Middle Lias of Raasay, in the north of 

 Scotland, and was obtained likewise, by Mr. R. Tate, in the zone of Ammonites spinatus 

 (Middle Lias), at Kettleness in Yorkshire. It has been collected from several other 

 Liassic localities in England, and upon the Continent ; and Mr. Tate would refer the 

 specimens found at Mickleton and Chipping Campden to the zone of Am. capricornus. 

 Mr. C. Moore procured a fine specimen (PI. X, fig. 25) from the Lias at Limpley, Stoke. 

 Messrs. Chapuis and Dewalque state having found their L. sacculus in the " Macigno" 

 Lias of Aubange, near Bleid, in the province of Luxembourg ; but I have never been 

 able to compare a Belgian specimen with ours, and give the present identification on the 

 authority of Mr. R. Tate. 



Genus Discina, Lam. 



8. Discina latissima, Sow., sp. Dav., Sup., PI. X, figs. 16 — 19; and PI. XI, 



fig. 30. 



Patella latissima, J. Sew. Min. Con., vol. ii, p. 85, pi. cxsxix, figs. 1 — 5, October,. 



1816. 



Discina — Morris. Catalogue, p. 134, 1854 (but not from Oxford Clay). 



Spec. Char. Shell orbicular, thin, a little longer than wide. Upper valve slightly 

 conoid, of small elevation ; apex subcentral, sometimes faintly radiately striated to some 

 distance from the pointed extremity of the apex ; and the whole valve marked with more 

 or less strongly indented concentric ridges, separated by flattened interspaces of greater 

 or lesser breadth. Smaller or pedunculated valve not known. Dimensions variable ; 

 Sowerby's type measured 10 lines in length, by something less in width. 



Obs. This species was described by Sowerby, under the designation of Patella 

 latissima, from some crushed or flattened casts now in the British Museum (PI. X, fig. 17, 

 18). His figure 1 (18 of our Plate) is an incomplete flattened shell or impression on a 

 slab of brown clay, stated to be from Lincolnshire; his fig. 5 (17 of our Plate) is a cast 

 in a light yellowish compact limestone, stated to have been " found in a rolled mass 

 (erratic) among lumps of chalk, sandstone, and gravel, at Pakefield in Suffolk." 



Sowerby does not consequently assign any geological age to the rock which contains 

 his species, but he does not neglect to intimate that in the same rock is found his Lingula 

 ovalis, a species which geologists subsequently referred to the age of the Kimmeridge 



