28 PLACOS TYLUS, NEW CALEDONIA. 



lips broaden, exposing repeated lamina? of growth, the callosity on 

 the body whorl thickens greatly, supporting strong tubercles and 

 emarginations, whilst a roughening of the surface occurs on the 

 outer lip, almost amounting to an immature denticulation, and the pos- 

 terior angle of the peristome becomes much more acute, and is deeply 

 channeled. Great variability is also noticed in the state of the 

 umbilicus, this aperture in some cases becoming completely closed and 

 overlapped by the spreading laminae of the pillar lip. 



SPECIES OF NEW CALEDONIA AND THE LOYALTY Is. 



The terrestrial species attain their acme in this area, some of them 1 

 being the thickest and heaviest of all land shells. The- very close 

 relationship existing between the forms of New Caledonia proper 

 and those of the Loyalty Islands probably indicates that the whole 

 archipelago was united in comparatively recent times into one much 

 larger land mass, upon which the heavy typical group of Placostyhis 

 and the thin whitish Leucocharis were developed from the common 

 ancestral stock. The peculiar nepionic characters of the arboreal 

 Leucocharis show that it is not allied to Solomon or Fijian groups, as 

 Crosse held, but is an independent branch. 



The terrestrial species live in the woods, generally in cool, moist 

 places. They only crawl around after rains. Pairing occurs in 

 April, and elliptical eggs which in P. porphyrostomus measure 4 by 

 5 mill., and are pure white, are laid in a shallow pit, in a moist spot, 

 and covered with dead leaves. 



They hold an important place in the native cuisine, P. souvillei 

 being the chief species eaten in the south, P. porphyrostoimis around 

 Noumea. Properly prepared they recommend themselves to the 

 European palate, but are rather leathery and not easy of digestion, 

 according to M. Marie the young ones being softer, and not un- 

 likd Helix pomatia. 



The species are polymorphic to a degree, and their identification 

 is often excessively difficult and uncertain. There cannot be much 

 doubt that too many species have been described from specimens 

 which represent merely individual or racial variations; but it would 

 seem that forms of all stages of differentiation occur in bewildering 

 abundance, and in the apparent absence of conditions adverse to the 

 perpetuation of intermediate forms, there is more than the usual dif- 

 ficulty in the limitation of conventional species. 



