Complex sentence: The shell attains a much larger size than in the typical "meesoni" subspecies, has a smaller umbilicus, only one tenth the major diameter of the base, and the sculpture consists of stronger, more dense malleations, but the spiral striations are subobsolete.
Split into simpler sentences: The shell attains a much larger size than in the typical "meesoni" subspecies, has a smaller umbilicus, which is only one tenth the major diameter of the base. The sculpture consists of stronger, more dense malleations, but the spiral striations are subobsolete.