Why is Pisces first?

[-JKP-]

The small strip between the two Taurus images is similar to strips found in the folds of the bifolio f67-f68 and of the single folio f73, and is a kind of reinforcement that was sewn in at the time of the present binding. 

I learned this as part of the answer to a question related to the bifolio 67-68. From the images, one cannot be entirely certain whether this is one very wide sheet (widest of all in the MS), or two sheets sewn together and these were the two ends.
It turned out to be the first option.

Thanks for that piece of information René.