MOLLUSCA OF THE ' CHALLENGEB ' EXPEDITION. 329 



witb 6^ whorls, but with, a fully developed outer lip, itself an 

 aftergrowtli on an earlier lip-edge still existing within tlie 

 mouth ; the third has 6 whorls, but has the sharp thin edge 

 and undeveloped pillar-teeth of the ' Samarang ' specimen. Tlie 

 later development o£ the shell greatly detracts from the " sharply 

 defined pattern of lattice-work," the sculpture becoming much 

 less crisp, the elongation and contraction of the body-whorl dimi- 

 nishes the relative breadth, the increasing obliquity of the whorls 

 elevates the spire, and the subsutural canal ceases to be excavated 

 and becomes merely a small oblique shelf. All these changes 

 modify considerably the relations of this Volute to the Eocene 

 species referred to by Adams audEeeve, and also by Mr. Edwards 

 in his 'Eocene Mollusca' (Palteont. Soc), pp. 146, 155, and in 

 particular to V. crenulata, Lam. (see Edwards, p. 154, pi. xs. f. i.) ; 

 but while diminishing some features of distinction dwelt on by 

 these authors, they so strongly develop others, that the differ- 

 ence between the living and the fossil species stands out more 

 strongly than ever. The size and form are, indeed, so utterly dis^ 

 similar, as at once to constitute a marked distinction. At the 

 same time, the species does interestingly represent the older 

 forms, in shape and sculpture recalling V. digitalina, Lam., 

 V. crenulata, Lam., and V. elevata, Sow., perhaps in particular ; 

 the thickening and toothing of the outer lip resembles exactly 

 that of V. luetatrix, Solander, and V. ambigua, Sol., while the 

 toothing of the pillar is like that of V. nodosa, Sow. Of course 

 whatever generic value " Volutilithes " of Swainson may have, 

 Adams's definition of the genus as having a "columella with 

 numerous faint rudimentary or obsolete plaits ; outer lip thin, 

 simple," must be modified. It never suited more than one or two 

 of the fossil species, perhaps not even these ; it proves inaccurate 

 for the one living representative of the group except in its 

 immature state, 



Pbovooatob, n, gen. 



Shell smooth, fusiform ; having the apex of Ancillaria, the enamelled 

 suture oiBuUia, the pillar-folds of Valuta, and the sinus of Pleurotoma. 



I believe this very curious form to be essentially a Volute, in 

 which genus the group of Cj/mlmm, and forms like V. scapha, 

 G-mel., V. wiperialis. Lam., and many others present the sutural 

 sinus, while Zidona has the enamelled spire. The name of CJuillen- 



