X0306 4 2015-07-01 0 0000086264 Carbon Natural Gas Co CRBO 0001535264 AWM Investment Company, Inc. 527 MADISON AVENUE SUITE 2600 NEW YORK NY 10022 0 0 1 0 Common Stock 2015-07-01 4 S 0 20000 0.6205 D 10868889 I By Limited Partnerships This is a weighted average price. AWM Investment Company, Inc., a Delaware Corporation (AWM), is the investment adviser to Special Situations Fund III QP, L.P. (QP), Special Situations Cayman Fund, L.P. (Cayman) & Special Situations Private Equity Fund, L.P. (PE and together with QP and Cayman, the Funds). As the investment adviser to the Funds, AWM holds sole voting and investment power over. 7,540,556 shares of Common Stock of the Issuer (the Shares) held by QP, 2,217,222 Shares held by Cayman & 1,111,111 Shares held by PE. Austin W. Marxe (Marxe), David M. Greenhouse (Greenhouse) & Adam C. Stettner (Stettner) are the controlling principals of AWM. The reporting person disclaims beneficial ownership of the Shares, except to the extent of its pecuniary interest therein. This report shall not be deemed an admission that the reporting person is the beneficial owner of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose. Adam Stettner 2015-07-07