ADDENDA. 105 



transversalibus instructs ; latere inferiore anfractibus planatis ; lineis transversalibus et 

 longitudinalibus cancellatis ; apertura siibquadrata. 



Shell discoidal, the superior and inferior sides concave, the back narrow, rounded, 

 encircled upon its upper part by two rows of tubercles, of which there are about nineteen in 

 a volution ; the upper surface has the volutions slightly concave, and traversed transversely 

 by obscure varices, proceeding from the tubercles ; the lower side is but little more con- 

 cave than the other ; the volutions are flattened. The entire surface of the shell has deli- 

 cate transverse and encircling lines, forming a regularly reticulated surface ; the aperture 

 is subquadrate. 



A beautiful and remarkably discoidal species. 



Geological Position and Locality. The Great Oolite of Hampton Cliffs ; in the collec- 

 tion of W. Walton, Esq. 



PLEUROTOMARIA BATHONICA, Lye. Tab. XLV, fig. 10. 



Testa trochiformi, conoidea, spira apice obtuso, anfractibus convexis lineis transversis et 

 perpendicularibus, sub-eequalibus, cancellatis; ultimo anfractu supcrne tuberculato-nodosis ; 

 sinu maffno, fascia sinus, plana, transversim lineata, in baso anfractuum sita ; ultimo an- 

 fractu basi piano, concentrice lincalo ; umbilico subnullo, apertura siibquadrata. 



Shell trochiform, conoidal ; spire obtuse; volutions convex, with cancellated transverse 

 and perpendicular lines ; the last volution with a row upon the upper part of nodose 

 tubercles ; the sinus is large, the fascia of the sinus is flattened and transversely lineated ; 

 the base is flattened, and concentrically lineated ; the aperture is subquadrate ; there is no 

 umbilicus. 



The encircling lines, of which there are three or four above the fascia of the sinus, are 

 more prominent than the perpendicular lines. The height is one third less than the basal 

 diameter. 



Geological Position and Locality. The Forest Marble of the Box Tunnel, near Bath ; 

 in the collection of W. Walton, Esq. 



PLEUROTOMARIA BURTONENSIS, Lye. Tab. XLV, fig. 8. 



Testa trochiformi, conoidea, anfractibus (5 6), superne itijlatis, nodoso-unaulatis, inferne 

 subplanis ; superficie lineis transversalibit* ct perpendicularibus, (eqi/alibus t dense cancellatis, 

 anfractu ultimo basi concentrice et radiatim lincatis, subconvexo, umbilico subnullo; xi/iti 

 mayno, in medio anfractuum situ ; fascia sinus delicate cancellatis. 



Shell trochiform, conoidal ; volutions (5 6), very convex in their upper parts, and 

 nodosely undulated; their lower portions rather flattened; the surface, with encircling and 



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