The newest clam shell is built
A) on the outside so the periostracum is the newest material.
B) on the inside so the inside nacreous layer is the newest.
C) both directions outward from the central prismatic layer.
D) all at once; all layers of shell are the same age.
E) None of the choices are correct

Question

Quizplus · Accepted Answer

The inside nacreous layer is the newest because it is continuously secreted by the mantle tissue of the clam as it grows. The outer periostracum layer may also be replaced periodically but is not as reliable an indicator of the newest growth layer.

The Newest Clam Shell Is Built