ADDENDA. 101 



Shell small, inflated ; spire elevated ; volutions (4) very convex, their posterior portions 

 nearly horizontal, their anterior portions convex, with the sutures deeply impressed ; the 

 last volution very large and ovate ; the aperture oval, no umbilical depression ; the surface, 

 with lines encircling and perpendicular, very densely and irregularly arranged, having 

 sometimes an imperfectly punctated aspect. 



It is allied to Turho gihhosus, D'Orb., but the latter is shorter and more inflated. 



Geological Position and Locality. The Forest Marble of Farleigh j in the collection 

 of W. Walton, Esq. 



MoNODONTA COMMA, Lyc. Tab. XLV, figs. 24, 24 «. 



Testa ovafo-discoidca, anfractibtis (4), clevatis, subplanis, suturis distinctis, anfractu 

 ultimo mayno, apertiira elliptica,uml)ilico p)arvo, dente basili mayno obtuso ; siiperficie striis 

 concentricis temiissimis, reyularibus. 



Shell ovate, discoidal ; spire elevated ; volutions (4) rather flattened, apex obtuse ; the 

 sutures distinct ; the last volution large, rather depressed, aperture elliptical ; umbilicus 

 small ; basal tooth large, obtuse ; the surface has very delicate, closely arranged, regular 

 encircling striations. 



The general figure nearly approaches to Monodonta (Crossostoma) heliciforme, but the 

 latter shell is without ornamentation, and has a smaller and more depressed basal tooth 

 and sulcus. 



Geological Position and Locality. The Forest Marble of Farleigh ; in the collection 

 of W. Walton, Esq. 



Monodonta Waltoni, Lyc. Tab. XLV, figs. 31, 31 «, b. 



Testa crassa, ovoidea, tenuissime concentrice striata, spira- brevi depressa, suturis 

 distinctis, ajifractibus (5) angustis, subconvexis, anfractu ultimo permagno ; basi obliquo 

 subumbilicato, dente et sulco magna obtuso ; apertura ovata. 



Shell thick, ovoidal, delicately concentrically striated ; spire short, depressed ; volu- 

 tions (5) narrow, slightly convex, their sutures distinct, the last volution very large, base 

 oblique, and slightly umbilicated ; the basal tooth and sulcus prominent ; aperture ovate, 

 outer lip thick. 



A pretty little delicately ornamented species, of twelve examples the smallest is 

 scarcely larger than the head of a pin, and has a distinct umbilicus ; the largest has a 

 diameter of four lines. 



Geological Position and Locality. The Forest Marble of Farleigh ; in the cabinet of 

 W. Walton, Esq. 



