CHAP. IV. ANCmLARIA. MABGINELLA. 133 



the aperture is only effuse, and the spire as much length- 

 ened,, as inLamprodoma: the plaits on the pillar, like 

 those on Volutilithes, are reduced to their minimum; the 

 two last are the strongest, the others nearly obsolete. 

 It is by this particular group that the VOLUTID^ and 

 the TURBINELLID.E are united ; the direct passage being 

 marked by Olivella biplicata Sw. in one, and Pseudoliva 

 plumbea Sw. in the other, (fig. 3. at p. 82.) The 

 olives are among the best known, the most polished, and 

 the most variable shells in this family. They swarm in 

 the seas of tropical climates, more especially in the 

 East, but seem altogether excluded from the European 

 coasts. 



(120.) The forms, or variations, among the ANCIL- 

 LARIN.E are as yet too few to render it necessary to 

 create sub-divisions : the beautiful analogy which this 

 group bears to the Purpurince, by the prominent little 

 tooth on the outer lip, as well as by the width of its 

 aperture, must not be overlooked ; while the high polish 

 of all the species, the general shortness of the spire, and 

 the unusual thickness of the base of the inner lip, are 

 so many points of resemblance to the Cyprceidce. 



(121.) Finally, the MARGINELLID^E are the smallest 

 shells, as to size, in the whole family : they are at 

 once distinguished by their thickened outer lip ; but they 

 all vary in the absence or developement of the spire 

 and of the inner lip, as well as in the plaits of the 

 pillar : hence their genera may be sufficiently defined. 

 Their union with the Volutince, by means of Scaphella 

 Zebra*, is clearly shown by our genus Glabella, where 

 the inner lip is either entirely wanting or but slightly 

 developed : these latter conduct to Volutella, which, by its 

 obsolete spire, preserves a strong analogy to the melons. 

 In Persicola we have a prototype of Concehelix; while 

 the typical form, Marginella, has the inner lip so much 

 developed, as to form a thickened deposition all round 

 the aperture. On the fifth type we feel some uncer- 



* Placed among the MarginelUe by Lamarck. 

 K 3 



