20 



All the inner volutions are covered by the last whorl, excepting onlj* 

 their umbilical faces. Outer whorl nearly flat, or only slightly convex 

 at the sides ; periphery narrowly rounded and obtuse; inner edges of the 

 volution oblique, almost confluent with the sides, the point of junction 

 being marked by a faint, rounded shoulder. Aperture narrowly ellip- 

 tical, deeply emarginate by the preceding volution. The height of the 

 aperture, as measured where the emargination is deepest, is more than 

 twice its width. Umbilicus small, shallowly funnel shaped, rather 

 deeply conical in the centre, but spreading rapidly and obliquely in 

 the outer whorl, especially near the mouth. Umbilical margin almost 

 obsolete, sutures (of the volutions) indistinct, not excavated or chan- 

 nelled. 



Surface marked by very faint and inconspicuous, transversely radiat- 

 ing plications. These are undulating, broad and rounded, but not much 

 raised, and are about equal in width to the shallow!}" concave depressions 

 which separate them. The folds are most prominent on the outer half 

 of the sides ; they seem to be obsolete on the periphery and are certainly 

 80 on the inner faces of the whorls. 



The adult and unique specimen figured on Plate II. is much 

 water-worn on the only side in which the septation is visible, and 

 the finer ramifications of the sutures have been obliterated. There 

 are indications of six or seven lobes in the septum nearest the 

 mouth, and of these the four or five inner ones appear to have 

 been simply toothed but not branched. Those placed near the peri- 

 phery do not seem to have been very complicated in their structure. 

 The "chamber of habitation" occujjies nearl}^ thi-ee-fourths of the outer 

 whorl. 



Grreatest dianieLer, three inches and nine lines : width of umbilicus, as 

 measured from the junction of the sides with the inner sm-face of the 

 body whorl, nine lines ; or, from suture to suture, five lines. Height of 

 apertm'e, at the point where the emargination is greatest, one inch and 

 nine lines: greatest width of do., ten lines. Depth of emargination of 

 the outer whorl, eleven lines. 



lYhen the drawings were made, nearly the whole of one side of the 

 fossil was covered by a nodule of shale. After the plates which contain 

 figures of this sjiecies were printed, the matrix was removed from the 

 specimen, and some new information was thus obtained which has been 

 incorporated into the above description. The outline of the aperture 

 (figure la) was found to be- incorrect in two particulars. First, the 

 emargination is not nearly deep enough, and secondly, the peripheiy, 



