CERITUIUM. 103 



Shell slender, pupoid, turrited. The spiral angle ranges from about 20° at 

 the opening to 13° in the anterior portions of the spire. Whorls numerous, 

 narrow and flattened. Sutures distinct. The subapical whorls are ornamented 

 by three granulated spirals, which in the anterior whorls are increased to the 

 number of five or six. The spirals undulate and decussate, with short and not 

 prominent costse at regular intervals, producing a very pretty basket-shaped 

 pattern. There is some irregularity in the development of these spirals, the 

 nodulations of the upper row being always the strongest. 



The body-whorl is about one-third the length of the shell, compressed, and 

 with ornaments similar to those of the spiral whorls (in the figured specimen 

 these have suffered from wear). Aperture subquadrate, with a short, stout 

 anterior canal. 



Relations and Distribution. — Closely related to the limasforme section of the 

 group. Specimens somewhat resembling G. Georgii occur in the Corallian of 

 England and possibly also in the Great Oolite. We may regard such either as 

 distinct species, or as megalomorphs of the prevailing form. Named after 

 Mr. George, curator of the Northampton Museum. Rare in the Lincolnshire 

 Limestone. 



87. Cerithium subcostigerum, sp. nov. Plate IX, fig. 11. 



Description : 



Length . . . .8 mm. 



Width . . . .275 mm. 



Shell short, subpupseform, slightly turrited; number of whorls about seven, 

 subconvex, and separated by a wide and shallow suture. Apex obtuse. The 

 ornaments consist of numerous fine spiral lines, so fine as to be scarcely visible in 

 the upper part of the whorls. These are decussated by robust costce, which 

 extend from suture to suture, being, however, strongest towards the posterior 

 margin of each whorl. These costje have a kind of twist from left to right, and 

 do not follow in true sequence, 



The body-whorl somewhat exceeds one-third the total length of the shell, and 

 its flanks are similarly ornamented. Base full, spirally striated, but without any 

 axial lines. Aperture subquadrate; other indications wanting. 



Relations and Distribution. — This species has some resemblance to Exelissa 

 (Kilvertia). On the other hand, it also has relations to some varieties of the 

 limseforme- group, where the tuberculations have a tendency to fuse throughout 

 into axial costoe. Only found, to my knowledge, in the Lincolnshire Limestone. 



