98 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
_ The unusual number of the volutions and the sudden inflation of the last volution 
renders its discrimination easy. 
The height is about equal to the transverse diameter of the last volution. 
Geological Position and Locality. Collected by E. Witchell, Esq., in the Great Oolite 
of Bussage, near Bisley Common; it has also occurred rarely in the Corbrash of 
Scarborough. 
Rissomna susunata, Lyc. Tab. XLI, fig. 9. 
e 
Testa elongata, subcylindrica, anfractibus (9) convexis, altis, longitudinaliter oblique 
costellatis, costellis, crebris (circa 30 in ambitu), apertura ovato-obliqua, parva. 
Shell elongated, subcylindrical, volutions (9) convex, high, longitudinally obliquely 
costellated, costellee closely arranged (about 30) in a volution; aperture ovate, oblique, 
small. 
A slender, subulate, delicately ornamented shell; the height of the volutions is equal to 
three fourths of their opposite diameter. 
Geological Position and Locality. The Forest Marble of Laycock ; in the collection of 
W. Walton, Esq. 
Rissomna (?) tumipuLA, Lyc. Tab. XLIV, fig. 13. 
Testa ovato-tumidula levigata, spira elevata, anfractibus (5) convewis, latis, suturis bene 
distinctis, apertura ovata, antice angulata, labro externo crasso. 
Shell ovate, inflated, smooth; spire short, but elevated; volutions (5) convex, wide, 
their sutures deeply impressed ; aperture ovate ; the outer lip thick, forming an angle at 
its junction with the base of the columella. ‘There is no distinct notch. 
A short, inflated species, resembling in the figure of the aperture 2. /evis, Sow., both 
seeming to constitute aberrant examples of Rissoina, and approximating to Rissoa. 
Geological Position and Locality. Collected by E. Witchell, Esq., in the Great 
Oolite of Bussage, near to Bisley Common, Gloucestershire. 
Nerita cLavatTuLa, Lyc. Tab. XLV, fig. 3. 
Testa hemispherica, spira parva, subdepressa, anfractu ultimo permagno, inflato, tuber- 
culis parvis, remotiusculis, per series quinis, regularibus, et lineis radiantibus, tenuibus, 
decussatis ; basi carina una, levigata. 
Shell hemispherical ; spire small, obtuse, and rather depressed ; the last volution very 
