140 



Type. Australian Museum. 



Shell globosely conoid, whorls rounded, spire elev^ated, base 

 rounded, aperture subcircular, umbilicus narrow. Diam. maj. 8, 

 min. 7, alt. 6, mill. 



Hah. The western flanks of Mount Ledgbird. 



The two latter forms are considered by Mr. Brazier to be species, 

 an opinion from which I differ with much reluctance. 



13. Placostylus bivaricosus, Gaskoin, 1854. 



Illustrations. Gaskoin, P.Z.S., 1854, pi. 29, ligs. 4, 5 ; Gassies, 

 Faune conchyliologique de la Nouvelle Caledonia, pi. 3, fig. 2. 



Descriptions. Gaskoin, P.Z.S., 1854, p. 152 ; Gassies, Faune 

 conch, de N. Cal., p. 47 ,; Pfr., Mon. Hel. Viv., Vol. iv., p. 447 ; 

 Crosse, Journ. de Conch. 1864, p. 128 ; Brazier, Aust. Mus. 

 Mem. 2, p. 27. 



Type. British Museum (?) 



Hob. All over the island in sheltered places under stones ; 

 abundant. 



The auriculoid Bulimi form so natural a group, limited in geo- 

 graphical range, beai'ing a most characteristic shell and sharply 

 defined by its dentition from the typical Bulimi that it appears 

 more convenient to accord Placostylns specific rank than to reduce 

 it as in Fischer's Manual to a section of Bnliiimlus. This species 

 speaks eloquently of a recent land connection extending on the 

 one side to New Caledonia and on' the other to New Zealand. It 

 is confined to Lord Howe Island and, the Loyalty Island habitat 

 quoted by Crosse is erroneous. This shell is as variable as any 

 of its polymorphic genus ; were the extreme forms only available 

 for study, two recent and another extinct species would be recog- 

 nised by all schools of conchologists. 



Jaw (pi. xxi., fig. 4) folded, kidney-shaped, thin, membranous, 

 margins recurved, ends angled, folds asymmetrical, about 14 on 

 each side, oblique, enclosing a triangular median space, scarcely 

 denticulating either margin. Radula (pi. xxii., fig 3) tongue shaped 

 three times as long as broad ; formula, 127 rows of 35 : 22 : 1 : 22 

 : 35 ; rachidian furnished with a slender median lance cusp whose 

 cutting point projects beyond the basal plate, half way along the 

 reflection are seated two small auxiliaiy cusps ; the lateral main 

 cusp is ovate, stouter and blunter than that of the rachidian and 

 also surpasses the posterior margin of the basal plate, the inner 

 auxiliary cusp is suppressed and the outer increased, the alate 

 margin of the basal plate is almost falcate ; the laterals pass 

 gradually into the marginals whose main cusp diminishes and 

 becomes double headed. 



These observations agree with those of Fischer on P. porphy- 

 rostomus undi P. scai^abus, Journ. de Conch., 1871, Vol. xix., pp. 



