[Illustration: FIG. 24.--_Roccus lineatus._ Inferior view of cranium. 1. Vomer. 4. Frontal. 7. Epiotic. 9. Pterotic. 11. Exoccipital. 13. Parasphenoid. 16. Alisphenoid. 3. Prefrontal. 5. Sphenotic. 8. Supraoccipital. 10. Opisthotic. 12. Basioccipital. 15. Prootic.] =Names of Bones of Fishes.=--In the study of the names of the bones of fishes it will be more convenient to begin with a highly specialized form in which each of the various structures is present and in its normal position. To this end we present a series of figures of a typical form, choosing, after Starks, the striped bass (_Roccus lineatus_) of the Atlantic coast of the United States. For this set of plates, drawn from nature by Mrs. Chloe Lesley Starks, we are indebted to the courtesy of Mr. Edwin Chapin Starks. The figures of the striped bass illustrate a noteworthy paper on "The Synonymy of the Fish Skeleton," published by the Washington Academy of Sciences in 1901. =Bones of the Cranium.=--The _vomer_ (1) is the anterior part of the roof of the mouth, armed with small teeth in the striped bass and in many other fishes, but often toothless. The _ethmoid_ (2) lies behind the vomer on the upper surface of the skull, and the _prefrontal_ (3) projects on either side and behind the ethmoid, the nostrils usually lying over or near it and near the nasal bone (51). Between the eyes above are the two _frontal_ (4) bones joined by a suture. On the side behind the posterior angle of the frontal is the _sphenotic_ (5) above the posterior part of the eye. Behind each frontal is the _parietal_ (6). Behind the parietal and more or less turned inward over the ear-cavity is the _epiotic_ (7). Between the parietals, and in most fishes rising into a thin crest, is the _supraoccipital_ (8), which bounds the cranium above and behind, its posterior margin being usually a vertical knife-like edge. The _pterotic_ (9) forms a sort of wing or free margin behind the epiotic and over the ear-cavity. The _opisthotic_ (10) is a small, hard, irregular bone behind the pterotic. The _exoccipital_ (11) forms a concave joint or condyle on each side of the _basioccipital_ (12), by which the vertebral column is joined to the skull. The _parasphenoid_ (13) forms a narrow ridge of the roof of the mouth, connecting the vomer with the basioccipital. In some fishes of primitive structure (_Salmo_, _Beryx_) there is another bone, called orbitosphenoid, on the middle line above and between the eyes. The _basisphenoid_ (14) is a little bone above the myotome or tube in which runs the rectus muscle of the eye. It descends toward the parasphenoid and is attached to the prootic. The _prootic_ (15) is an irregular bone below the ear region and lying in advance of the opisthotic. The _alisphenoid_ (16) is a small bone in the roof of the mouth before the prootic. These sixteen bones (with a loose bone of specialized form, the _otolith_, within the ear-cavity) constitute the cranium.