ODOXTOCETI. 561 



Cetacea. The maxilla is produced in front of, but not over, the orbital pro- 

 cess of the frontal. The lacrymal bone is distinct and the tympanic is anky- 

 losed with the periotic. The rami of the mandible are convex outwards, and 

 the space between them is greater than the width of the rostrum ; they 

 are connected by ligament at the symphysis. The ribs articulate with 

 the ends of the transverse processes, the capitular part being imperfect 

 and not reaching the centrum. The sternum is short and articulates 

 with only one pair of ribs. Olfactory nerves and a small olfactory organ 

 are present. 



The family includes the right -whales and the rorquals or fin-whales. 



Balaena L., right-whales, skin of throat smooth, no dorsal fin. B. 

 tnifftticetus L., Greenland or Arctic right -whale ; Arctic Ocean ; from 

 45 to 50 feet ; 380 baleen plates or more, the longest 10 to 12 feet. 

 B. australis Desmoul., the southern right-whale, temperate seas of both 

 hemispheres ; smaller head and shorter baleen ; has been so much pursued 

 that it is now very scarce. Several extinct species in the Pliocene of 

 Europe and America. Neobalaena Gray, skin of throat smooth, a small 

 dorsal fin, to 20 feet, baleen very long and white, 1 species, N. marginata 

 Gray, New Zealand and Australian seas. Rhachianectes Cope, 1 species, 

 R. glaucus, the grey whale of the X. Pacific. Megaptera Gray, with 

 dorsal fin, skin of throat plicated and long pectoral fins. M. boops L., 

 hump-back whale, 45 to 50 feet, Atlantic and Pacific ; several Pliocene 

 species. Balaenoptera * Lacep, rorquals, head small, skin of throat 

 plicated, dorsal fin present, body long and slender, cervical vertebrae 

 free ; in all seas ; whalebone inferior and blubber scanty. B. sibbaldi 

 Gray, blue whale, the largest known, to 85 feet ; Atlantic, Arctic Oceans. 

 B. musculus L., common rorqual, 65 to 70 feet, Atlantic and Arctic ; and 

 many other species ; many extinct species from the Pliocene. Several 

 extinct genera from the Miocene onwards, e.g. Cetotherium Brandt, Herpe- 

 tocetus v. Ben., Plesiocetus v. Ben., etc. 



Sub-order 2. ODONTOCETI (DELPHINOIDEA). 



In the toothed-whales, conical calcified teeth, often in great 

 number, are always present after birth. The external nares are 

 united to a single semilunar opening, and saccular dilations 

 lying between the skin and the skull are developed in the passage 

 which connects the opening with the narial passages. The upper 

 surface of the skull is more or less asymmetrical, and the superior 

 maxillary bone is posteriorly expanded and spread out over the 

 supraorbital process of the frontal. The nasal bones are reduced 

 to mere nodules, and take no part in roofing over the narial 

 passage. Lacrymal absent except in the Physeteridae. Tym- 

 panic not ankylosed to the periotic. Rami of the mandible 

 straight and meeting in a symphysis. Anterior ribs two-headed. 

 Sternum usually composed of several pieces and connected with 

 several ribs. Manus always pentadactyle. Caecum absent. 



* v. Beneden, Les Balenopteres, etc., Mem, Cour. Ac. Belg., 41, 1888. 

 Z. II. O O 



