EXHIBIT 99.1 January 31, 2018 XTO Energy Inc. 810 Houston Street, Suite 2000 Fort Worth, TX 76102  Re:

Underlying Properties (100%) Relating to the
Cross Timbers Royalty Trust As of December 31, 2017SEC Pricing Case
 Gentlemen: At your request, Miller and Lents, Ltd. (M&L) estimated the proved reserves and future net revenues as of December 31, 2017,
attributable to the XTO Energy Inc. (XTO) interest in certain oil and gas properties prior to inclusion in the Cross Timbers Royalty Trust, i.e., Underlying Properties (100%). The Underlying Properties (100%) include royalty interest and working
interest properties from which net profits interests were conveyed to the Cross Timbers Royalty Trust. The properties consist of approximately 3,172 leases and 16,439 wells and are located primarily in New Mexico, Oklahoma, and Texas. The report was prepared for the use of XTO in its financial and reserves reporting and was completed on January 31, 2018. M&L
performed evaluations, which are designated as the SEC Pricing Case, using price and expense premises specified by XTO and described in detail on Attachment 1. The aggregate results of M&Ls evaluations are as follows:  Net Reserves


Future Net RevenuesReserves Category

Oil andCondensate,MBbls.


Gas,MMcf


Undiscounted,M$


Discounted at10% per Year,M$Royalty Interest PropertiesProved Developed Producing


1,110.7



18,825.4



102,715.0



51,637.7Subtotal


1,110.7



18,825.4



102,715.0



51,637.7Working Interest PropertiesProved Developed Producing


1,224.0



499.2



18,459.2



10,633.1Subtotal


1,224.0



499.2



18,459.2



10,633.1Total Working and Royalty Interest PropertiesProved Developed Producing


2,334.7



19,324.6



121,174.2



62,270.8Total Proved


2,334.7



19,324.6



121,174.2



62,270.8 Proved reserves and future net revenues were estimated in accordance with the provisions contained in
Securities and Exchange Commission Regulation S-X, Rule 4-10(a). The Securities and Exchange Commission definition of proved reserves is shown on Attachment 2 (not
included). Gas volumes for each property are stated at the pressure and temperature bases appropriate for the sales contract or state regulatory authority; therefore, some of the aggregated totals may be stated at a mixed pressure base. No
provisions for the possible consequences, if any, of product sales imbalances were included in M&Ls projections since M&L received no relevant data. Estimates of future net revenues and discounted future net revenues are not intended
and should not be interpreted to represent fair market values for the estimated reserves. In M&Ls projections, future costs of abandoning facilities and wells were assumed to be offset by salvage values. Estimated costs, if any, for
restoration of producing properties to satisfy environmental standards are beyond the scope of this assignment. Following Attachment 2
(not included) is a list of exhibits that include annual projections of future production and net revenues for each reserves category, interest type, and state. Also included in the exhibits are one-line
summaries showing the proved reserves and future net revenues for each property in the total royalty




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XTO Energy Inc.

January 31, 2018
Page 
 2  trust, in the working interest category, in the royalty interest category, and in each state. Projections of individual property future production and net revenues are included in separate
volumes to this report. These exhibits and volumes should not be relied upon independently of this narrative. The proved developed
producing reserves and production forecasts were estimated by production decline extrapolations, water-oil ratio trends, P/Z declines, or in a few cases, by volumetric calculations. For some properties with
insufficient performance history to establish trends, M&L estimated future production by analogy with other properties with similar characteristics. The past performance trends of many properties were influenced by production curtailments,
workovers, waterfloods, and/or infill drilling. Actual future production may require that M&Ls estimated trends be significantly altered. Reserves estimates from volumetric calculations and from analogies are often less certain than
reserves estimates based on well performance obtained over a period during which a substantial portion of the reserves was produced. The
data employed in M&Ls estimations of proved reserves and future net income was provided by XTO. The current expenses for each lease were obtained from operating statements provided by XTO except for certain leases where XTO deducted items
considered by XTO to be nonrecurring expenditures. No overhead was included for those properties operated by XTO. For some properties, such as large waterfloods, XTO assumed a decline in operating costs due to depleting production that was derived
by forecasting a decrease in the property well count. The data provided to M&L by XTO, including, but not limited to, graphical representations and tabulations of past production performance, well tests and pressures, ownership interests,
prices, and operating costs, were accepted as represented and were considered appropriate for the purpose of this report. M&L employed all methods, data, procedures, and assumptions considered necessary and appropriate in utilizing the data
provided to prepare this report. The evaluations presented in this report, with the exceptions of those parameters specified by others,
reflect M&Ls informed judgments and are subject to the inherent uncertainties associated with interpretation of geological, geophysical, and engineering information. These uncertainties include, but are not limited to, (1) the
utilization of analogous or indirect data and (2) the application of professional judgments. Government policies and market conditions different from those employed in this study may cause (1) the total quantity of oil, natural gas
liquids, or gas to be recovered, (2) actual production rates, (3) prices received, or (4) operating and capital costs to vary from those presented in this report. At this time, M&L is not aware of any regulations that would affect
XTOs ability to recover the estimated reserves. Miller and Lents, Ltd. is an independent oil and gas consulting firm. No director,
officer, or key employee of Miller and Lents, Ltd. has any financial ownership in XTO Energy Inc. or any related company. M&Ls compensation for the required investigations and preparation of this report is not contingent on the results
obtained and reported, and we have not performed other work that would affect M&Ls objectivity. Preparation of this report was supervised by Katie M. Reinaker, P.E., an officer of the firm who is a licensed Professional Engineer in the
State of Texas and is professionally qualified, with more than nine years of relevant experience, in the estimation, assessment, and evaluation of oil and gas reserves. M&Ls work papers and data are in our files and available for review upon request. If you have any questions regarding the above, or
if M&L can be of further assistance, please call. Yours very truly, MILLER AND LENTS, LTD. Texas Registered Engineering Firm No. F-1442  By

/S/ KATIE M. REINAKERKatie M. Reinaker, P. E. Senior Vice
President
 KMR/jj




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XTO Energy Inc.

January 31, 2018
Page 
 3  Attachment 1 Cross Timbers Royalty
Trust (100%) SEC PRICING CASE  A.

Oil Price

Average price during the 12-month period prior to 12/31/17 determined as the arithmetical average of the first-day-of-the-month price for each month during the year 2017. The average price was based on the West Texas Intermediate benchmark price. The arithmetical
average of the first-day-of-the-month benchmark price is $51.34 per barrel and is held
constant through the life of the property. The average realized price, after appropriate adjustments, is $47.08 per barrel.B.

Gas Price

Average price during the 12-month period prior to 12/31/17 determined as the arithmetical average of the first-day-of-the-month price for each month during the year 2017. The average price was based on the Henry Hub benchmark price. The arithmetical average of the first-day-of-the-month benchmark price is $2.98 per MMBtu and is held constant through the life
of the property. The average realized price, after appropriate adjustments, is $3.14 per Mcf.C.

Operating Costs

Current expenses held constant through the life of the property. For some properties, expenses included a variable component that was a constant cost per unit of gas production and a fixed component that was a constant cost per well
completion.D.

Discount Rate

10% per year.