48 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
is silicified, and is a beautiful object for the delicacy of its ornamentation ; the original 
specimen figured by me in the ‘ Annals and Magazine of Natural History,’ was obtained 
by the Rev. P. B. Brodie in the shelly freestone of the Inferior Oolite at Leckhampton 
Hill; at each locality it ranks as one of the more rare productions. 
Triconia ciytuia, D’Orbigny. Tab. XXXVI, fig. 2; Tab. XL, figs. 5, 5 a. 
TRIGONIA CLYTHIA, D’Orbigny. Prodr. de Paléont., i, p. 309. 
“ Coquille singuliére par ses cotes concentriques formant de deux en deux un angle sur 
la region anale, independamment de la area costulée en travers.” (D’Orbigny.) 
Testa subtrigona, conveaa, transversim costata, costis numerosis, crebris, curvatis, 
postice alternatim angulatis, carina marginal levigato, elevato, ared planatd transversim 
costatd, costis magnis, depressis. 
Shell subtrigonal, convex, transversely costated; costae numerous, small, closely 
arranged, curved, convex upon their lower and coneave upon their upper sides; the first 
few costee are united to the marginal carina, the succeeding costa are bent suddenly 
upwards at their posterior extremities, forming a series of angles, one of which proceeds 
from every second costa; the marginal and inner carinz are smooth and elevated; the 
area is moderately wide, flattened, traversed transversely by a few large depressed and 
waved costa, which are interupted by an oblique mesial furrow. 
The general figure is nearly triangular; the umbones are mesial, much elevated and 
pointed ; the anterior border is nearly straight, sloping obliquely downwards, but slightly 
sinuated immediately beneath the umbones; the posterior border is short and oblique. 
Dimensions —The height and the lateral diameter are nearly equal; the diameter 
through both the valves is one fifth less. 
The coste upon the sides of the valves are so closely arranged that about twenty 
occur in a specimen seven lines in height. 
Geological Positions and Localities. The Great Oolite of Minchinhampton and Bisley 
Commons, also in the upper zone of the same formation near to Bath. Luc (Calvados). 
Triconia ScarsurceEnsis, Lyc. Tab. XXXVII, fig. 1. 
Testa ovato-trigona subdepressa, elongata, umbonibus recurvatis, margine antico rotundo, 
postico excavato, producto; area angusta, elongata, carinis tribus delicatissimis ornato ; 
valvis costis tuberculatis, magnis per series leviter arcuatis, antice parvis, trregularibus, 
postice magnis curvatis. 
Shell ovately trigonal, rather depressed, elongated ; umbones recurved ; anterior side 
rounded and produced ; posterior slope somewhat concave, lengthened ; the area is narrow, 
flattened, with irregular transverse striations, and ornamented with three very delicate 
