cartilaginous fish, Chondrichthyes; and jawless fish, Agnatha. The discipline can include the biology, taxonomy and conservation of fish, as well as husbandry and commercial fisheries.

Now at my very feet lay the link to the fossil Agnatha, the earliest (jawless and cartilaginous ... seen attached to the flank of one kind of fish or another. (The well-versed "Derby Boughs ...