XXVlll GEOGRAPHIC DISTRIBUTION. 



b". Seven-ribbed, the ribs lower and splitting toward aperture ; 

 length 19 mill., nearly 7 times the greatest diam., 



bednalli, p. 248. 



a'. Minute longitudinal striae on the smaller end, the rest smooth ; 

 length 76 mill., about 18 times the diam., novcehollandice, p. 93. 

 a," No longitudinal sculpture. 



b. Length 11 mill., about 9 times the greatest diam. ; aper- 

 ture very oblique, wider than long; surface obliquely 

 wrinkled, platyceras, p. 126. 



b'. Decidedly larger, more slender, polished, 



leptosceles, lubricatum, erectum, p. 110, 111. 



New Zealand. 



Five species of Dentalinm are credited to this province, one of 

 which is a doubtful member of the fauna, and two others of uncer- 

 tain standing (see synopsis below). All are confined to the prov- 

 ince. No Cadulus or Siphonodentalium have yet come to light. 



a. Shell smooth, white, nearly straight; length 15 mill., about 9 

 times the diam., ecostatam, p. 102. 



a'. Shell with longitudinal ribs. 

 b. Principal ribs about 18. 



c. Eighteen unequal ribs at aperture, fewer at apex ; 

 length 15-16 mill., about 6 times the diam., 



huttoni, p. 71. 



c/ Eighteen ribs, with intervening riblets, all becoming 



subobsolete at aperture ; shell nearly straight, rapidly 



tapering; slit short; length 56 mill., about 7J times 



the diam., opacum, p. 70. 



b'. Thirty or many ribs ; length 57-60 mill., 7 or 8 times the 



diam., zelandicum, pacificum, p. 70. 



Habitat unknown. 



The habitats of the following are unknown : D. cnrtum, dipsyche, 

 aculeatum, dacostianum, translucidum, ambiguum, longum, fistula and 

 multistriatum. There are also a few others, of which the assigned 

 localities are more or less doubtful. 



Geologically the group is an old one. Dentalium first appears in 

 the Lower Silurian ; though it must be noted that part of the Silu- 

 rian species, such as some of those described by Eichwald, are very 

 doubtful members of the group, presenting bizarre sculptural char- 



