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. 



TRIGONIA CLTTHIA, D'Orbigny. Tab. XXXVII, fig. 2 ; Tab. XL, figs. 5, 5 a. 

 TRIGONIA CLTTHIA, TfOrbigny. Prodr. de Paleont., i, p. 309. 



" Coquille singuliere par ses cotes concentriques formant de deux en deux un angle svr 

 la region anale, independamment de la area costulee en travers." (D'Orbigny.) 



Testa subtrigona, convexa, transversim costata, costis numerosis, crebris, curvfifi-s, 

 postice alternatim angidatis, carina marginali leevigato, elevato, area planatd transversim 

 costata, costis magnis, depressis. 



Shell subtrigonal, convex, transversely costated ; costae numerous, small, closely 

 arranged, curved, convex upon their lower and concave upon their upper sides ; the first 

 few costae are united to the marginal carina, the succeeding costze are bent suddenly 

 upwards at their posterior extremities, forming a series of angles, one of which proceeds 

 from every second costa j the marginal and inner carinse are smooth and elevated ; the 

 area is moderately wide, flattened, traversed transversely by a few large depressed and 

 waved costae, 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 costae 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). 



TRIGONIA SCARBURGENSIS, Lye. Tab. XXXVII, fig. 1. 



Testa ovato-trigona subdepressa, elongata, umbonibus recurvatis, margine antico rotunda, 

 postico excavato, producto ; area angusta, elongata, carinis tribus delicatissimis ornato ; 

 valvis costis tuberculatis, magnis per series levifer arcuatis, antice parvis, irregular ibus, 

 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 



