62 MOLLUSCA FROM THE GREAT OOLITE. 



T. Testa turbinatd; spird data; anfractibus (5) suhconvexis, longitudinaliter costatis; 

 costis 12 rectis elatis; basi leevi; aperturd parvd, dcpressd. 



Shell turbinated ; spire elevated ; whorls (5) rather convex, longitudinally costated ; 

 costae straight, elevated, smooth, about 12 in a volution ; the base smooth ; the aperture 

 small and depressed ; the sutures of the whorls are strongly marked. Axis 3 lines, basal 

 diameter 6 lines. 



Locality. The specimen figured is rather flattened ; it occurred in the planking of 

 Minchinhampton Common, and is more acutely conical than that figured by M. d'Archiac, 

 of which it is considered to be only a variety. 



Trochus Ibbetsoni. Plate X, figs. 4, 4a. 



T. Testa conicd, spird elatd, obtusd; anfractibus (5 — 6), lavigatis et plants, aut sub- 

 convexis; aperturd depressd, obliqud; umbilico nullo. 



Shell conical ; spire elevated, obtuse ; whorls (5 — 6) smooth and flattened, or slightly 

 convex ; aperture depressed, oblique ; no umbilicus , columella lip thick and excavated. 



This species somewhat resembles T. Dunkeri, from which it differs in the more elevated 

 spire, obtuse apex, and somewhat convex form of the whorls ; the base is, likewise, more 

 convex and narrow : in the larger specimens these distinctive characters become more 

 prominent, and the sutures of the whorls are strongly marked. It occurs together with 

 T. Dunkeri, but in smaller numbers. 



Locality. Eastscombs and Bussage. 



The name in compliment to Capt. L. L. B. Ibbetson, F.R.S., whose geological surveys 

 of the different railways have been of considerable interest to science. 



Troohus sqtjamiger. Plate X, figs. 2, 2a, b. 



T. Testa conicd; apice obtuso; anfractibus (6 — 8) subcompressis, suturis impressis; 

 anfractibus cingulis quaternis tubulososquamosis ; cingulo inferiori minimo; basi plana et 

 IcBvi; aperturd depresssd; umbilico nullo. 



Shell conical ; apex obtuse ; whorls (0) rather compressed, the sutures well marked ; 

 whorls with four circles of nodules or plications which are squamosely tubular or excavated 

 towards the aperture, the lowest circle of nodules being much the smallest ; the base is flat 

 and smooth ; the aperture depressed ; no umbilicus. 



In this species the height exceeds the basal diameter. It occurs not very unfrequently 

 in the planking, a rock which usually adheres very closely to shells, and the plications 

 become entangled with the particles of stone, so as to render good specimens very rare. 



Locality. Minchinhampton. 



