ODOXTOCETI. 563 



blend posteriorly in the normal mammalian fashion ; Platanista Wagl., 

 the maxillae are much expanded posteriorly and arched upwards so as 

 nearly to inset above the narial openings, blind eyes vestigial without 

 lens ; 8 feet, feeds on small fish and Crustacea, Ganges, Brahmaputra, 

 a7i<l Indus. Inia D'Orb., 1 feet, Upper Amazon. Pontoporia Gray, 

 5 feet, mouth of the Rio de la Plata. Extinct genera, Argyrocetus Lyd., 

 Eocene, Patagonia ; Pontistes Burm., and Pontivaga Am., U. Eocene, 

 Argentina ; and other genera from the Miocene and Pliocene of Europe 

 and America. 



Fam. 5. Delphinidae. The teeth are numerous in both jaws except 

 in the narwhal ; the rostrum is of moderate length and the symphysis 

 of the mandibles does not extend for more than one-third the length of 

 the lower jaw ; the maxillae and f rentals are not markedly produced 

 upwards at their edges ; lacrymals not distinct ; pterygoids frequently 

 meet. Anterior ribs two-headed, posteriorly they lose their capitula 

 and remain articulated to the transverse processes only. Sternal ribs 

 ossified. A large group of living forms, found in all seas, many will ascend 

 rivers in search of food ; about 19 genera and 50 to 100 species ; extinct 

 species of existing genera from the Miocene onwards. 



FIG. 289.Delphinus del-phis (Rdgne animal). 



A. Head rounded, without distinct beak ; rostrum about as long as cranium. 



MonodonL,., the narwhal, the entire dentition (save for some irregular 

 vestiges) is suppressed except two large teeth in the front of the maxilla ; 

 one (the left) of these, and sometimes both, project in the male as long 

 (7 to 8 feet), spirally grooved tusks ; in the female they both remain in 

 the alveolus ; a second pair of small teeth has been detected behind the 

 tusks in the foetus ; pterygoids wide apart ; cervical vertebrae mostly 

 distinct; with distinct neck and no dorsal fin ; 1 species. M. monoceros L., 

 the use of the tusk is unknown, Arctic Ocean ; there is a Pliocene species. 

 Delphinapterus Lacep., like the last, but without tusks, dentition : 



8 to 10 



the only species, D. leucas Pall, the white-whale or beluga, 12 feet, 

 Arctic seas ; Miocene and Pliocene species are known. Neomeris Gray, 

 Indian Ocean. Phocaena Cuv., porpoise, dentition f|, teeth with com- 

 pressed crowns ; both this and the previous genus sometimes possess a 

 patch of small horny tubercles on the back * ; three species ; Ph. corn- 

 munis Cuv., feeds on fish, Atlantic and Pacific, not Mediterranean. Cepha- 

 lorhynchus Gray, about 3 species. Orcella Gray, Indian Ocean and Irra- 

 waddy, 1 species. Orca Gray, the killer, white and yellow on black, to 



They are also found on the head and front of the flipper, and dermal 

 calcifications are found in connection with them. Kiikenthal, Anal. 

 Anz. 5, 1890, p. 237. 



