CEPHALOPODA FROM THE HOKKAIDO. 15 



"Bei meinem grössten Stück, das über einen Fuss im Durch- 

 messer hielt, und von dem ich nur ein Bruchstück mitgebracht 

 habe, ist der Steinkern der äussersten Windung ganz glatt, nur 

 über and über mit ineinander gewirrter Lobenzeichnung bedeckt ; 

 die erwähnten dichteren Bippen sieht man an nächst der inneren 

 Windung des nämlichen Stücks." 



The smoot state of the outer volutions of the older indivi- 

 duals, as above referred to, is very common also in the Japanese 

 species of Pachydiscus, but has never yet been observed in the 

 Gaudryceras, occurring very abundantly in the Hokkaido and 

 sometimes also in Amakusa. 



The writer is now acquainted w^ith nine species and five 

 varieties of Gaudryceras from the Hokkaido, all of which belong to 

 the category known as 'the group of Gaudryceras Sacya.^ This 

 group is again divisible into six subgroups, chiefly according to 

 the character of the full grown shells. 



I. Subgroup of Gaudryceras tenuiliratum Yabe. 



This subgroup is characterized by the full-grown whorl having 

 numerous ribs of two kinds, a number of narrow^er ribs being 

 inserted between each pair of broader ribs. The latter on a closer 

 examination are found to be made up of two or three finer ribs 

 placed close together. The whorls grow" exceedingly rapidly in 

 height and breadth. 



The type is G. tenuiliratum^^ from the upper Ammonite beds 

 of the Hokkaido and is very variable in form. G. varayurense 

 Kossriat"^ sp. probably belongs to this subgroup, and G. mite 



1) Vide p. 19. 



2) Kossmat: 1. c. p. 2G (122), PI. IV (XVIII), fig. 2 a, h, c; PI. Ill (XVII), fig. 9. 



