22 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



MoNODONTA ExiGUA, Lyc. Tab. XLIV, fig. 29. 



Testa jmrva ovata, spira data, obtusa, anfractibus tribus, subplanis, anfractu ultimo 

 rotundo ; striis tenuibus cingendis, costisque obliquis depressis, crebris, decussatis ; apertura 

 ovata, columella ad basin incrassato, subumbilicato. 



Shell small, ovate; spire elevated, obtuse; volutions three, very slightly convex, the 

 sutures distinctly marked ; the last volution rounded with densely arranged, delicate, 

 encircling striations, which are decussated upon the upper and middle portions of the 

 volution by numerous depressed, oblique costae, which are rendered somewhat granular by 

 the striations ; the aperture is ovate, the columella is thickened at its base, and there is a 

 slight umbilical depression ; the base of the last volution is destitute of costse. 



Geological Position and Locality. The Great Oolite of Minchinhampton Common, 

 collected by Mr. Witchell. 



MoNODONTA Lycetti, W/titeuves, MSS. Tab. XXXI, figs. 14, 14 a. 



Testa subdepressa, spira brevi, exserta ; anfractu ultimo permagno lateribus planatis, 

 costisque magnis, crenulatis, cingendis, basi constricta sulcb magno. 



Shell depressed ; spire short and slightly mammillated, the last volution very large, 

 angulated at its upper margin, flattened upon its sides, and slightly convex towards the 

 base, which has a large, encircling furrow ; the aperture is moderately large, wide above, 

 contracted towards the base ; the columella is rounded and very tumid. 



The whole shell is encircled with rows of rope-like crenulated costse, the upper border 

 and flattened sides being formed by three costge larger than the others ; beneath these are 

 five costae diminishing symmetrically to the basal furrrow ; the upper surface, which is 

 flattened, has three encircling costae, within which rises a small, mammillated apex. 



Lateral diameter one fourth greater than the height. 



The large, rounded costae, flattened sides, and depressed figure, readily distinguish 

 it from allied species. 



Geological Position and Locality. In soft, pale, gray, marly limestone (Bradford 

 Clay?), Islip, Oxon., collected by J. F. Whiteaves, Esq. 



MoNODONTA SPARSISTRIATA, Lyc. Tab. XLV, fig. 9. 



Testa parva turbinata, depressa, spira anfractibus 4 ; covexiusculis, striis 6, cingendis ; 

 apertura ovata, basi subpland, lavigato, nmbilico nullo. 



Shell small, turbinated, depressed ; spire moderately elevated, consisting of four rather 



