COI.I.IER : THK SRCTIOX PI.ACOSTYl.rS OF THE CEXl'S TlL'T.nrnS. 209 



rubbed smooth, only in quite young specimens can be recognised a 

 regular punctuation, as the remnant of a hairy covering rubbed away. 

 The last whorl is large, frequently pressed together from the front 

 towards the t)ack as in Auyicida. The spire is twisted and carries an 

 oblique fold, which is often very strongly projecting. The mouth is a 

 long oval, often irregular, and narrowed by folds and teeth. The rim 

 of the mouth is more or less thickened, spread out, or slightly reflected. 

 The two margins are united by a callus, which frequently carries on 

 the middle a deep standing knob or tooth. The rim of the columella 

 is broad and appressed. These large Auricuia-\\\i& BuUiui form one 

 of the most interesting groups, in the richness of their forms, of the 

 whole genus. 



Their geographical boundary is notably of the sharpest, at least if 

 we take the series in my sense, that is to say, including Charts, 

 Aspoittis and Eiimecostjlus, — New Caledonia, the Fiji Islands, the 

 Solomon Islands, and the south-eastern part of the New Hebrides. One 

 or two out-lying species are found in the North Island of New Zealand, 

 perhaps vestiges of a very old connection between the land, more 

 probably carried about by travellers in very early times. This com- 

 prises the whole of the Placostylus district. Njt otily are these shells 

 missing from the continent of Australia, and also in New Guinea, 

 according to the present state of our knowledge, but also in the Bismarck 

 Archipelago on the one side, and Tonga and Samoa on the other side, 

 however much the fauna of these groups of islands may be related in 

 other respects with those of the Fiji and Solomon Islands. 



AVithin this district there prevail, the genuine Placostyli, with thick 

 shells, living on the earth {Euplacostylus Crosse), in New Caledonia, 

 and there attain their greatest development, whilst in the Fiji Islands 

 are prevalent the thinner-shelled, tree-inhabiting C/iaris, but they do 

 not include one another, because as a rule most groups are connected 

 with each other through intermediate forms. Conchologically the 

 boundary is an extremely sharp one with the next section oi Bulimus 

 {Amphidroiims) which in Bulimus Janus pushes forward a representa- 

 tive into the Placostylus district, this shell being found in the New 

 Hebrides. 



Placostylus has conchologically no relations with Amphidromus, 

 although the soft parts, according to Semper's investigations, are very 

 similar, on the other hand, some /Vrtrt'ii^'// approach considerably two 

 South American groups, in form and habit, and that in two directions, 

 both to the large Bonis (various toothless Placostyli, such as F. 

 bavayi) as also to the smaller Bulimulidas of the section Drytnceus 

 (such as pancheri and loya'tyensis). An appearance, which under 

 certain circumstances, could be employed m favour of the hypothesis 

 of the whole of the Pacific Ocean, having once being taken up by a 



o 



