THE VALIDITY OF CHAETODERMA-MONTEREYENSE HEATH ALONG WITH CH-ARGENTEUM HEATH (MOLLUSCA, CAUDOFOVEATA)

The northeastern Pacific aplacophoran mollusk species Chaetoderma arge nteum, Ch. attenuatum, and Ch. montereyense (Caudofoveata), diagnosed by HEATH (I 91 1) and recently synonymized as a single species Ch. arg enteum Heath, are reexamined. Detailed analysis of the type material r eveals (1) that Heath's description of Ch. attenuatum refers to a spec imen of Ch. montereyense, and (2) that Ch. attenuatum is anatomically (pericardium and other characters) and geographically (Alexander Archi pelago, south Alaska) identical with Ch. argenteum only. Thus, Ch. att enuatum can be synonymized with Ch. argenteum, whereas Ch. montereyens e (off Santa Barbara, California to Vancouver, B.C.) is to be maintain ed as a valid species.