This pattern is from a book called "zoomigurumi 3". I adjusted the shell pattern, switching colours between each round, to get this spiral effect.
The book is really nice, well written. I've made a couple of other pattern from it and enjoyed each one!
i don' know much about crocheting, but my mon does this as a hobby and we had this book when i grew up. i have like 10 of these cats varying in size and colour.
anyways, cute turtle. very nice work.