32 ART. 2. H. Y A BE : CRETACEOUS 



Dimensions : — 



■Ratio . 



Diameter. 7.2 cm. 100. 



Height of the last whorl. 3.0 „ 41. 



Breadth of the last whorl. 2.8 „ 38. 



Height of the W'liorl last but one. 1.2 ,, 16. 



Breadth of the whorl last but one. 1.4 ,, 19. 



Width of umbilicus. 2.4 „ 33. 



Inner volutions broader than high ; wdien 4.0 cm. in 

 diameter, they are as high as broad, after which they rapidly in- 

 crease in height, so that a cross-section near the mouth of the 

 larger individual shows a subquadrate form, higher than broad, 

 being broadest near the umbilical edge, but narrowing toward 

 the rounded ventral side. A change also takes place in the 

 surface sculpture, just as in G. ienuiliratum and G. crassicostatum. 

 The surface is at first covered with numerous very fine striœ and 

 about five periodic ribs, corresponding to the feeble furrows on 

 the cast. The striœ and the ribs are slightly S-shaped as is 

 usual in shells of this genus. These periodic ribs appear more 

 frequently when the shell has attained a diameter of about 5 cm. 

 The figured specimen shows 7 of them on the last quarter of the 

 last whorl. The suture line of our specimen when compared 

 wâth that shown in fig. 6 b, PI. VI. of Jimö's w^ork, is î-dv more 

 finely toothed. 



The relation of this species to G. denseplicatimi Jimbô sp. 

 has been already alluded to. It does not appear, at first sight, 

 to be different from the subgroup of G. temdliratum, and it is 

 commonly not easy to distinguish the former from the finely 

 sculptured variety of the latter. The main points in which they 

 differ lie in the fact that the suture line in G. sfriatum is more 

 finely divided than in G, tenuilirahmi, and the thicker ribs and 



