59 
Ornament reaches acme at 45 mm., then declines. Smooth from 90 mm. 
on. Table showing number of ribs in a quadrant of whorl at various 
stages. 
Diameter 
16 mm. 8 primaries 13 secondaries 
30 “ 6 “ 16 
62 « 7 “ 15 
and 17 peripheral knots 
Venter rounded up to 5 mm. at which it becomes fastigate. It develops a 
knotted keel at about 15 mm. Loses its knots about 85 mm. becoming 
more acute. A true knife-edge from 90 mm. onward. Mouth border 
Figure 4. Anacardioceras perrini sp. nov.; correlation of diameter and number of whorls. 
inclined and rostrate. Conch form, complicated — an oxygastric contracti- 
ellipti-oxycone. The species differs from the genotype in having the 
primary rib furcation nearer the umbilicus: about one-third way across the 
