I've come across shell stitch patterns and instructions in a variety of different publications. Shell stitch instructions were included in vintage Peterson's magazines dated 1855, 1858 and 1859, among others.
Don't worry, you won't have to hunt for old crochet instruction manuals at your local antique store; you can learn how to crochet the shell stitch right here on our website, for free.
Free Crochet Patterns Using Shell Stitch:
The shell stitch is a nice stitch for using with many different types of projects, but it's especially nice for edgings and afghans.