62 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
Minchinhampton Opis allied to O. /vnulatus is distinct from the typical Inferior 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 Lucrensis, D’Ord. Tab. XL, figs. 19, 19 a. 
Oris Luciensts, D’Orbigny. Prodrome, i, p. 307, No. 106. 
Testa subtrigona, postice acute carinata, umbonibus prominentibus acutis, lunula per- 
magna, profunda, levigata, inferne rostrata, area posteriora sulco obliquo wnstructo ; 
superficie striis tenuibus 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 O. 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. 
Geological Position and Locality. The Great Oolite of the Box Tunnel, near Bath, in 
the collection of W. Walton, Esq. 
Corsuta atrenvata, Lyc. Tab, XXXVII, figs. 6, 6a. 
Testa convera, parva, subequilatera, transversa, longitudinaliter, subtillissime striata ; 
latere posteriore attenuato, rostrato, producto ; angulo obliquo instructo; basi leviter 
eurvato, 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. 
