Page:Natural History, Fishes.djvu/318

304 some or other of which are scattered over all seas. Fifteen are enumerated among British Fishes, either as habitual residents in our waters, or as accidental stragglers. Considerable difficulty is felt by naturalists in the attempt to subdivide the family into natural groups; not from the number of the species so much as from the diversities of form and structure that exist among them. The following is the arrangement proposed by Mr. Swainson.

1. Zygænina. The Hammer-heads. These have