CHEMNITZIA. 257 



anterior termination a decussation similar to, yet less decided 

 than, that of the preceding whorls. The aperture ranges 

 from oval to pyriform, and occupies from one-fourth to one- 

 fifth (more frequently the latter) of the entire length of the 

 shell ; its breadth is fully one-half of the basal diameter. 

 The pillar lip is rather long, simple, narrow, scarcely 

 oblique or curved, erect posteriorly, and somewhat effuse 

 in front, where a slight angularity is observable at its 

 junction with the basal arcuation of the outer lip. The 

 largest individual we have seen only measured two 

 lines and a quarter in length, and about half a line in 

 breadth. 



The two principal varieties are distinguished by the 

 flatness and comparative rotundity of their volutions. In 

 the latter the essential sculpture is less defined, but the 

 flexuosity of the ribs is more apparent, and sometimes there 

 is a vestige of an umbilical chink ; in the former the 

 front portion of the base is almost always smooth, and the 

 suture looks as if it were excavated, from the abrupt and 

 slightly angulated inward shelve of the lower end of each 

 whorl. The degree of convexity of the outer lip is regu- 

 lated, of course, by that of the spire. 



Mr. Jeffreys has communicated many localities for this 

 variable species. It seems to range from the laminarian 

 zone to as deep as forty fathoms or more. It occurs 

 though rarely and locally all around the shores of the 

 British Islands, and ranges to the Mediterranean. It 

 has been found by Mr, Searles Wood in the coralline 

 crag. 



VOL. III. 



