382 MURICIDiE. 



a rather smaller basal one additionally encircle the body. 

 The form, tliough very variable, being sometimes narrow 

 and elongated, sometimes squat and broad, is more or less 

 oval, swells out nearly in the middle, and attenuates con- 

 siderably and nearly equally at both extremities. The 

 spire occupies on the average about two-sevenths of the 

 dorsal length, but does not preserve an elevation in exact 

 proportion to the increased or diminished length of the final 

 whorl ; it is usually remarkably short where the body is 

 broad, and often is much produced when the body is 

 peculiarly narrow : similarly the aperture in the former 

 will occupy nearly five-sevenths of the length, in the latter 

 merely one-half, or even less. The entire exterior is 

 covered with not much elevated narrow convex spiral 

 ridges (there are generally three or four of these on the 

 penult and preceding volution, and about fifteen — but the 

 number is uncertain — on the final whorl), that are so 

 closely disposed as only to be separated by a broadish 

 sulcus (for, where the space permits, it is filled up by a 

 narrower costella). In general the surface is merely 

 obscurely traversed lengthway by almost obsolete wrinkles, 

 or indistinct waves of increase, but occasionally the corru- 

 gations rise in numerous fringe-like imbricating lamelUe 

 that form vaulted scales where they overhang the re- 

 volving ridges. A fine and simple suture divides the 

 whorls, which taper above, are of fast longitudinal in- 

 crease (the penult is moderately high for the most i)art), 

 are more abruptly perpendicular below, and much more 

 shelving above, where in some of the more produced forms, 

 especially upon the body-whorl, the surface is flattened or 

 even retuse : sometimes the projection of an upper ridge 

 causes the smaller volution to appear angulated. The 

 apex is small, and is somewhat irregularly twisted. The 



