As commenters bruxer and Lydia Fletcher worked out, January’s crocodile mystery showed a detail of the head of a dos-à-dos binding, with a covered board running down the middle separating two gauffred text blocks. The full picture makes it a bit clearer:
A dos-à-dos binding is one in which two books are bound together back-to-back (giving rise to the name), so that each has its own front cover, but a shared back board. If you’re looking down at the head of the book—the top edge of the binding, as shown above—you see the text block of each book and the s-shape of the binding curving from top board across spine to bottom board then across spine and then to top board again. If you were to look at the fore-edge of a dos-à-dos binding, as on the left below, you’d see both the fore-edge of one text block and the spine of the other.
The metallic look of the board running down the middle of the head is caused by the embroidered border of the binding (click on the images to enlarge them). This is a very decorated volume—it’s a little bit hard to see, but the edges of the pages of this book are gauffred and gilt (that is, they’ve been decorated by cutting designs into them and then gilded).
So, it’s pretty and all, but why would you want to have a book bound like that? For one thing, it’s a handy way of keeping together two books that you use in tandem. The typical dos-à-dos binding holds together a New Testament and a Book of Psalms—the Folger has 7 17th-century dos-à-dos bindings, 5 of which are NT/Psalms combinations. If you think about how these books would be used together in the period, moving back and forth between them, housing them in a single binding this way makes sense. It treats the books as a unit that can be easily navigated by quickly finding the beginning of each work. It’s the navigation factor that is part of this structure’s advantage over a sammelband, in which different works follow each other in sequence in a single binding. A sammelband is great for some things, but unless you have multiple bookmarks allowing you to rapidly find the beginning of each book, there’s no physical demarcation between them. Another structural advantage of dos-à-dos bindings is that they aren’t too fat to open—anyone who’s worked with a tightly bound book or with an overly hefty book knows how hard it can be to open the volume wide enough to read it comfortably. In a sammelband, the thickness of the spine is the cumulative thickness of all the books; in a dos-à-dos binding, the thickness of each spine is only as thick as an individual book.
So, if 5 of the 7 are of New Testaments and the Psalms, what are the other two dos-à-dos books in the Folger’s holdings? One is a 1631 edition of John Taylor’s Verbum sempiternum, a teeny-tiny book (64mo format! 45 mm height!), one half of which is a thumb bible of biblical paraphrases of the Old Testament and the other half of the New Testament. Although this isn’t exactly the same thing as joining together a New Testament with a Book of Psalms, it certainly makes sense to present the two parts of the thumb bible this way.
And the 6th book? That’s the one we’re looking at for our crocodile. It’s made up of two works: STC 2406, The psalter or Psalmes of Dauid, after the translation of the great Bible, pointed as it shall be said or sung in churches: with the morning & euening praier, and certaine additions of collects, and other the ordinarie seruice, gathered out of the booke of Common praier. Also a briefe table declaring the true vse of euerie Psalme, made by Master Theod. Beza. Newlie printed in a final and portable volume or manuel, and STC 2544.2, The whole booke of Psalmes: collected into English meeter by T. Sternhold, I. Hopkins, and others. In other words, if you open it from one side, you have the Psalms, and if you open it from the other side, you have . . . the Psalms.
So this is where I turn the mystery back to you again, dear Readers. Why would two books of the Psalms be bound together this way? Since the Folger’s copy is in a fragile embroidered binding, I haven’t tried to examine it myself. The Folger’s catalog doesn’t indicate that either of the two incomplete. And there’s not a copy of STC 2406 on EEBO to look at, nor does that version of the Psalms exist in another edition, so I’m not sure how it might differ from the Sternhold and Hopkins. So, any thoughts on what’s going on here?
As an advance thank-you for your thoughts, I’ll leave you with a couple of related goodies. First, although most dos-à-dos bindings are of two books, it is possible to have more than two bound together: see this example of a 5-fold 1736 binding from AbeBooks. Less pretty, perhaps, but more useful, is my second offering: if you’re looking for some help with the terminology used in this post and in other discussions of books, the 8th edition of John Carter and Nicholas Barker’s ABC for Book Collectors (2004) can be found online, thanks to Oak Knoll Press and the International League of Antiquarian Booksellers.