Some that I caught and examined closely had, as Scott says, "vermiculate marks on the back very plain and distinct."
vermiculate: worm-like in form: a marking with wormlike tracings.
What a breeding nest of vermiculate cares and pains was this human heart of ours!
He regarded the thing as vermiculate, and ready to corrupt the obedience.
Religion itself in the hearts of the unreal, is a dead thing; what seems life in it, is the vermiculate life of a corpse.
My life seemed only a vermiculate one, a crawling about of half-thoughts-half-feelings through the corpse of a decaying existence.