10 ART. 2. — H. YABE : CRETACEOUS 



Dimensions : — 



Rntio. 



Diameter. 20.0 em. 100. 



Height of the last whorl. 8.0 „ 40. 



Breadth of the last whorl. 7.5 ,, 37. 



Height of the whorl last but one. 2.8 „ 14. 



Breadth of the whorl last but one. 3.2 ,, 16. 



Width of umbilicus. 7.0 „ 35. 



Shell discoidal, composed of many round whorls, increasing 

 rather rapidly in height and breadth. AVhorls nearly round, 

 somewhat laterally compressed on the last volution, but elsewhere 

 rather inflated, being broader than high. Umbilicus very wide, 

 surrounded by a perpendicular wall which gradually passes to 

 the lateral side of the whorls ; the outer volutions embrace the 

 inner ones only to a small extent. Surflice covered with very 

 numerous, transverse, fimbriate striae, close to one another, at 

 intervals of about two m.m. on the last volution, without any 

 trace of periodic arrest of growth. Ribs flat, scarcely elevated, 

 the cast of the interior being quite smooth. 



Suture line shows three saddles and corresponding lobes 

 on each side of the siphonal line, regularly diminishing in size 

 toward the umbilical suture. Siphonal saddle elongate lanceolate 

 and serrated along the margin. External lobe considerably shal- 

 lower than the first lateral which is the broadest. External 

 saddle unequally bifid inclining somewhat inward ; first lateral 

 saddle also asymmetrically bipartite and larger than the external 

 one. Second lateral saddle very deeply bipartite, apparently 

 forming two separate saddles on the umbilical wall. All branches 

 of the saddles and lobes are repeatedly bifid and finely incised. 

 The branchlets along both sides of the siphonal saddle are asym- 

 metrically arranged, as shown in the accompanying figure. 



