ODONTOCETI. 



563 



blend '"posteriorly in tlie normal inammalian fasliion ; Platanista Wagl., 

 the maxillae are much expanded posteriorly and arched upwards so as 

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

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

 and Indus. Inia D'Orb., 7 feet, Upper Amazon. Pontoporia Gray, 

 5 feet, mouth of the Rio de la Plata. Extinct genera, Argyi-ocetufs Lyd., 

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

 Ai'gentina ; 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 sj'inphysis 

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

 the lower jaw ; the maxillae and frontals are not markedly produced 

 vipwards 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, fomid in all seas, many will ascend 

 rivers in search of food ; ab<Hit 19 genera and 50 to 100 species ; extinct 

 species of existing genera from tlie Miocene onwards. 



Delphinus delphis (Regne animal). 



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



Monodonh., 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 ^mkno^vn, Arctic Ocean ; there is a Pliocene species. 

 Delphinapterus Lacep., hke the last, but without tusks, dentition |-^JJ; 

 tlie 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 |4, teeth with com- 

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

 patch of small laorny tubercles on the back * ; three species ; Ph. com- 

 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, wliite and yellow on black, to 



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

 calcifications are fomid in connection with them. Kvikenthal, Anat. 

 Anz. 5, 1890, p. 237. 



