X0306 4 2017-11-01 0 0000086264 Carbon Energy Corp CRBO 0001687163 Yorktown XI Associates LLC C/O YORKTOWN PARTNERS LLC 410 PARK AVENUE, 19TH FLOOR NEW YORK NY 10022 0 0 1 0 Common stock, par value $0.01 per share 2017-11-01 4 M 0 432051 A 432051 I See Footnotes Warrant 2017-11-01 4 M 0 432051 D 2017-04-03 2024-04-03 Common Stock, par value $0.01 per share 432051 0 I See Footnotes Shares received upon exercise of Warrant No. 2, issued on April 3, 2017 (the "CAC Warrant") to Yorktown Energy Partners XI, L.P. ("Yorktown XI"). The consideration Yorktown XI paid for the full exercise of the CAC Warrant was the transfer and assignment to Carbon Natural Gas Company (the "Issuer") of 2,940 Class A Units of Carbon Appalachian Company, LLC, a Delaware limited liability company. These shares were inadvertently omitted from one Form 4 filed by the reporting person on April 9, 2018. These securities are directly owned by Yorktown XI. The reporting person is the sole general partner of Yorktown XI Company LP, the sole general partner of Yorktown XI. The reporting person disclaims beneficial ownership of these securities except to the extent of its pecuniary interest therein, and this report shall not be deemed an admission that the reporting person is the beneficial owner of the securities for Section 16 or any other purpose. Yorktown XI Associates LLC, /s/ Peter A. Leidel, Manager 2018-09-18