phins and, especially, Physeter. This asymmetry affects particularly the premaxillae, the maxillae, and the nasals. The base of the skull is symmetrical. The Whale's skull has very long premaxillae which, however, do not, except in the extinct
Fig. 184.—Under surface of the cranium of a young Caa'ing Whale (Globicephalus melas). × 1⁄5. AS, Alisphenoid; BO, basioccipital; cf, condylar foramen; ExO, exoccipital; Fr, supra-orbital process of frontal; gf, glenoid fossa of squamosal; Ma, body of malar; Mx, maxilla; OS, orbitosphenoid; Per, posterior (mastoid) process of periotic; Pl, palatine; PMx, premaxilla; Pt, pterygoid; Sq, squamosal; tg, deep groove on squamosal for meatus auditorius externus, leading to tympanic cavity; Ty, tympanic; Vo, vomer; ZM, zygomatic process of malar. (From Flower's Osteology.)
Zeuglodonts, bear any teeth. The nasal bones, whether symmetrical or the reverse, are very small in existing Whales, which arrangement, together with the long and broad maxillary bones, removes the anterior nostrils, the blow-hole, far backwards. The roof of the skull is not at all formed by the parietals externally. These bones form a portion of the side of the cranium, but are replaced or covered by the enormously-
