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                              April 20, 2021

       Adam Stone
       Chief Executive Officer
       ARYA Sciences Acquisition Corp III
       51 Astor Place, 10th Floor
       New York, NY 10003

                                                        Re: ARYA Sciences
Acquisition Corp III
                                                            Registration
Statement on Form S-4
                                                            Filed March 26,
2021
                                                            Amendment No. 1 to
Registration Statement on Form S-4
                                                            Filed April 7, 2021
                                                            FIle No. 333-254796

       Dear Mr. Stone:

              We have reviewed your registration statement and have the
following comments. In
       some of our comments, we may ask you to provide us with information so
we may better
       understand your disclosure.

              Please respond to this letter by amending your registration
statement and providing the
       requested information. If you do not believe our comments apply to your
facts and
       circumstances or do not believe an amendment is appropriate, please tell
us why in your
       response.

              After reviewing any amendment to your registration statement and
the information you
       provide in response to these comments, we may have additional comments.

       Registration Statement on Form S-4 filed March 26, 2021

       Did the ARYA Board obtain a third-party valuation or fairness
opinion...?, page viii

   1.                                                   We note the revised
disclosure in response to prior comments 1 and 7. With reference to
                                                        the disclosures on
pages 105 and 114-115, please revise the disclosure to clarify that the
                                                        Board valued Nautilus
based on the valuation of one company that the Board deemed
                                                        comparable.
       Background to the Business Combination, page 103

   2.                                                   Please revise to
disclose the date when ARYA received the Nautilus Forecasts.
 Adam Stone
ARYA Sciences Acquisition Corp III
April 20, 2021
Page 2
3.       Please revise the disclosure on page 105 to clarify whether the ARYA
Board or a third-
         party derived the $925 million valuation ascribed to Seer, Inc. and
whether this was a pre-
         or post-IPO valuation.
Certain Company Projected Financial Information, page 112

4.       We note the disclosure added to page 114 concerning the Board's
consideration of
         financial projections in a potential upside scenario. Please revise to
disclose whether
         these upside scenario projections were prepared by Nautilus or ARYA.
With a view to
         disclosure, please tell us whether the Board considered financial
projections in a potential
         downside scenario. Revise the Background to the Business Combination
section, if
         applicable, to indicate when any upside or downside scenario
projections were provided to
         the Board.
5.       We note your disclosure on page 112 indicating that the projections
reflect numerous
         qualitative estimates and assumptions. Please tell us, and if
applicable, revise to
         indicate, whether there were material qualitative estimates and
assumptions made
         beyond the stated expectation regarding adoption of a three-phase plan
for
         commercialization. Also revise to clarify the time frames for the
three phases underlying
         the disclosed projections.
6.       We note the disclosure that the Nautilus Forecasts were prepared
solely for internal use,
         capital budgeting and other management purposes, and were not intended
for third-party
         use, including by investors or holders. Please revise to clarify
whether the projections
         were intended for use by the AYRA Board.
Comparable Company Analysis, page 114

7.       Revise to indicate whether the Board used this analysis to calculate
an implied enterprise
         value for Nautilus as well as estimated EV/Revenue figures. Also,
include Nautilus in the
         table (or an adjacent one) to show Nautilus    Revenue and Revenue
Growth figures for
         these same years.
8.       Revise to clarify how the analysis in this section relates, if at all,
to the $925 million
         implied equity valuation of Seer, Inc., and how it supports a $900
million equity valuation
         for Nautilus.
9.     Please explain why the Board decided to use the valuation of a single
company as opposed
       to the median of the three highlighted companies that the Board
identified as similar life
FirstName LastNameAdam Stone
       sciences tools providers. Also, explain how the Board determined that
Seer, Inc. was the
Comapany
       mostNameARYA      Sciences Acquisition
             comparable company    as opposed toCorp
                                                 908III
                                                     Devices, Inc. If known,
please disclose the
       equity
April 20, 2021valuation
               Page 2 ascribed to 908 Devices, Inc.
FirstName LastName
 Adam Stone
FirstName   LastNameAdam
ARYA Sciences    AcquisitionStone
                             Corp III
Comapany
April       NameARYA Sciences Acquisition Corp III
       20, 2021
April 320, 2021 Page 3
Page
FirstName LastName
Material U.S. Federal Income Tax Considerations, page 154

10.      We note that the opinion of counsel, filed as Exhibit 8.1, is limited
to the "Effect of the
         Domestication on U.S. Holders". Please have counsel provide a tax
opinion that also
         covers the effects of Section 367(b), PFIC considerations, and the
effects of exercising
         redemption rights, or advise. Also it is unclear to us how an opinion
that addresses the
         effect of the Domestication is meaningful to investors where the
opinion is "subject to the
         PFIC" rules. In this regard, it appears that the tax consequences
depend upon the
         application of the PFIC rules and the company discloses that it likely
will be considered a
         PFIC for the current tax year. Refer to Section III.A.2 and III.C.3 of
Staff Legal Bulletin
         No. 19 for additional guidance.
        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

        Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration
statement.(202) 551-3652 or Vanessa Robertson at (202) 551-3649 if you have
questions
regarding comments on the financial statements and related matters. Please
contact Abby Adams
at (202) 551-6902 or Joe McCann at (202) 551-6262 with any other questions.



                                                               Sincerely,

                                                               Division of
Corporation Finance
                                                               Office of Life
Sciences
cc:      Peter Seligson, Esq.