MANGELIA. 459 



below. Eacli of the principal turns is adorned with 

 seven subangular (yet often rounded by attrition) lon- 

 gitudinal ribs that traverse the spire in almost continuous 

 lines, but do not extend to the lower half of the body- 

 whorl. They are rather broad-based, usually swell out 

 a little below, and are separated by concave intervals, that 

 are wider than the ribs themselves ; in very fine specimens 

 the concavities are almost obsolete on the lower half of 

 the penult turn. The surface, otherwise, seems smooth 

 to the eye, but with a magnifying glass one descries 

 most minute and densely disposed spiral striulai pervading 

 the entire exterior. A very fine and inconspicuous sutural 

 line winds between the seven or eight peculiarly flat turns 

 that compose the spire ; these taper regularly and rather 

 considerably above, are moderately high, of rather slow 

 longitudinal increase, and terminate in a bluntish apex. 

 In a peculiarly fine specimen, the body occupied three- 

 sevenths only of the dorsal length, in general it is as long 

 as the rest of the whorls united ; it is moderately at- 

 tenuated and somewhat compressed towards the base, 

 where the declination is gradual and not much rounded ; 

 from the flatness beneath the suture there is often (espe- 

 cially in the more aged shells), a kind of gibbous sub- 

 angulation near the middle. The mouth, which is devoid 

 of sculpture, usually occupies about two-fifths of the 

 ventral length ; it is of an elongated oval shape that is 

 contracted above to an acute angle, but is only narrowed 

 slightly anteriorly, where it forms a rather broad and very 

 short canal, that is neither recurved, nor leans to either 

 side. The throat is quite smooth, and is often tinged 

 with livid purple far within ; but the more exposed 

 portion of it, as well as the chief part of the pillar lip 

 is usually of a whiter cast than the external colouring. 



