61 
then spreading across the flank it finally extinguishes the ventral orna- 
ment. Conch form, a compressed sphaerocone from youth on. Flanks 
become convergent with maturity. Mouth border, plain, i.e., without 
lappets, strongly inclined, slightly swollen. A helically twisted umbilical 
Figure 6. Anacardioceras perrini sp. nov.; width of umbilicus (shown by a broken line) 
and thickness of whorls (by a solid line) of holotype expressed as fractions of 
the diameter. 
columella is present. Differs from other macrocephalitids in its early 
smoothness and narrow umbilicus. Differs from Buckmaniceras in septal 
line: L1>EL, LI has longer though less divergent branches; and in conch 
form. Septal line rather simple as late as early maturity. Resembles 
Buckmaniceras in its obtuse ornament. 
93289—5 
