ORDER CETACEA. 



1305 



the typical Z. cetoides being extraordinarily abundant in parts of the 

 latter country, where they have been weathered out of a deposit of 

 Middle Eocene age. 



Suborder 3. Odontoceti. — All living Cetaceans not included in 

 the Mystacoceti belong to this suborder, which is characterised by 

 the presence of calcined teeth after birth ; the functional ones being 

 generally numerous, but sometimes reduced to a single pair (occa- 

 sionally wanting). Baleen, or whalebone, is invariably absent ; the 

 cranium is more or less unsymmetrical ; the nasals are reduced to 

 mere bony nodules which do not roof over the narial passages ; the 

 lachrymal is either united to the jugal, or of very large size ; and 

 the mandibular rami are nearly straight, and meet in a median sym- 

 physis. The tympanic is not anchylosed to the periotic, and has 

 not the completely involuted structure found in the Mystacoceti. 



Family Physeterid^e. — In this family there are no functional 

 teeth in the upper jaw ; and the anterior facet of the periotic for 

 articulation with the tympanic is smooth (fig. 11 76), while the pos- 

 terior tympanic surface of the former bone is broad, with a distinct 

 median ridge. In recent genera some or all of the cervical vertebrae 

 are fused together. This family is divided into the two subfamilies 

 Physeterince and Ziphiince. In the former, which comprises the 

 existing Cachalot, or Sperm Whale (Physeter), and the Short-nosed 

 Cachalot (Cogia). the mandibular teeth are numerous and implanted 

 in a long groove partly divided by imperfect septa. Remains of the 

 gigantic Sperm Whale {P. macrocephalus) are found in the English 

 Forest-bed, and also in the Pleistocene of South America ; the large 

 teeth have no enamel at their summit. Allied to this genus are 

 Eucetus from the English and Belgian Crags, and Physetodon from 

 the Pliocene of Australia ; while Physeterula is a genus founded on 

 a whale from the former deposits, which does not exceed some 20 

 feet in length. A number of Pliocene and Miocene forms appa- 

 rently allied to the Cachalot, 

 but with the crowns of the 

 teeth tipped with enamel, have 

 been described as Ba!<znodo?i, 

 Scaldicetus, Hoplocetus, Physodon, 

 and Ziphioides ; Hoplocetus and 

 Physodon comprise comparatively 

 small species from the English 

 and Belgian Crags and the French 

 Miocene ; while Ziphioides is from ^^^^fZZ^J^t" 

 the Middle Miocene of Baltringen 



in Wiirtemberg. In the Ziphiine subfamily, comprising the existing 

 Bottle-nosed (Hyperoodon) and Beaked-Whales (Ziphius and Meso- 

 plodori), all the mandibular teeth, with the exception of one or 



