62 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



Minchinhampton Opis allied to 0. lunulatus is distinct from the typical Liferior Oolite 

 shell, and that D'Orbigny has correctly indicated its distinctive characters in the brief 

 sentence above quoted ; our figures in Part II, Tab. VI, faithfully represent the Great Oolite 

 species. 



Opis Luciensis, D'Orb. Tab. XL, figs. 19, 19 a. 



Opis Luciensis, IfOrhigny. Prodrome, i, p. 307, No. 106. 



Testa sultrigona, postice acute carinata, umhonibus prominentibus acutis, lunula per- 

 mac/na, profunda, IcBvigata, in/erne rostrata, area posteriora mho obliquo instructo ; 

 superjicie striis tetiuibus concentricis, interdum obsoletis. 



Shell subtrigonal, short, posteriorly acutely carinated, with a conspicuous, oblique sulcus 

 upon the post-carinal area ; the umbones are elevated, acute, moderately incurved ; the 

 lunule is very large and deeply excavated, occupying the entire anterior side; the surface 

 is smooth, with an acute, plain margin, its lower extremity forming a rostrated projection ; 

 the posterior surface of the valves has very delicate, concentric striations, which are only 

 partially visible. 



It is allied to 0. pulchella, but is shorter, less convex, the umbones are more prominent 

 and less incurved, the lunule is very much larger, the posterior keel more acute, the 

 surface more smooth. 



Geolopcal Position and Locality. The Great Oolite of the Box Tunnel, near Bath, in 

 the collection of W. Walton, Esq. 



CoiiBULA ATTENUATA, Lyc. Tab. XXXVII, figs. C, 6 a. 



Testa convewa, parva, subaquilatera, transversa, lonyitudinaliter, subtillissime striata ; 

 latere posteriore attenuato, 7'ostrato, producto ; anyulo obliquo instructo ; basi leviter 

 curvato, postice subsinuato. 



Shell small, convex, nearly equilateral, transverse, longitudinally very finely striated ; 

 anterior and posterior borders sloping obliquely downwards ; the posterior side is attenu- 

 ated ; it has an oblique angle, which separates a narrow posterior space ; its lower extremity 

 is rostrated -, the anterior lower extremity is elliptically curved ; the lower border is 

 lengthened, slightly curved, and posteriorly somewhat sinuated ; the umbones are small and 

 somewhat pointed. The figure is more elongated and has less convexity than the other 

 Great Oolite species of the genus ; the striations upon the posterior slope are bent 

 upwards at a right angle to their direction across the valve. 



Height, equal to two thirds of the length, and a third greater than the diameter through 

 both the valves. 



