# The Nature of Transition Circumstellar Disks I. The Ophiuchus Molecular Cloud ⋆ 

Lucas A. Cieza 1 , $^{2}$, Matthias R. Schreiber$^{3}$, Gisela A. Romero3 , $^{4}$, Marcelo D. Mora$^{3}$, Bruno 

Merin $^{5}$, Jonathan J. Swift$^{1}$, Mariana Orellana3 , $^{4}$, Jonathan P. Williams$^{1}$, Paul M. Harvey$^{6}$, 

Received ; accepted 

Neal J. Evans II 6 

To appear in ApJ 

