Here is a lovely grotesque book cover design by Morse that is not in my book, but was discovered in time for the Grolier Club exhibition. As you can see, it is signed AM under the author's name, within the curly leaves of the lower part of the design.
Below is a review of the design in The Bookman, Volume 4. The review also attributes Morse as a designer for some of the volumes in Century's 'Thumbnail Series' and for the singular, classical design of Harper's 'Odd Number Series' and includes a picture of A Venetian June. While we now know that Morse designed at least two of the books for The Thumbnail series (Writing to Rosina and Tracings [see Tracings in an earlier posting), it still remains for me to locate the rest of the books in the series and see which can be attributed to Morse.