456 coNiD^v. 



to, or nearly equal to, the rest united. The usual number 

 of the longitudinal ribs ranges from ten to fifteen on each 

 of the two principal turns ; they extend from the top to 

 the bottom of each volution, but are less thick and pro- 

 minent posteriorly : they are sometimes much more remote 

 than at other times, but are never very closely disposed, 

 are frequently a little slanting or curved, and almost 

 always, if not invariably, become obsolete upon the peaked 

 anterior extremity of the body, where the basal declina- 

 tion is gradual but convex. The rather close and some- 

 what irregular revolving striae are commonly less apparent 

 beneath the simple, yet profoundly impressed suture ; they 

 traverse the entire shell, yet from their shallowness are 

 more frequently (especially in at all worn examples) only 

 perceptible in the intervals of the ribs. The spire tapers 

 to a very blunt and more or less unsymmetrically coiled 

 apex. The whorls are not scalar, though at times they 

 shelve towards their upper suture in a somewhat subangu- 

 lated fashion ; they are convex or even slightly ventricose, 

 of rather slow longitudinal increase, and, except in the 

 elongated varieties, rather short than otherwise. The 

 mouth occupies, on the average, four-ninths of the ventral 

 length ; filling in the produced forms a lesser proportion, 

 in the broader abbreviated ones a greater proportion : it is 

 of a narrow oblong form, angulated above, and tapering 

 below into a rather short and broadish canal, the end of 

 which is not abruptly truncated, but somewhat rounded. 

 The outer lip, which is indented posteriorly by a rather 

 short and very shallow sinus, is acute at the edge, and 

 smooth internally : it is almost continuously arched, but 

 does not project very much, and is neither reflected nor 

 patulous. The edge of it advances a little in the middle, 

 and is scarcely interrupted in its sweep by the retusion 



