REPORT ON THE CETACEA. 41 



It is important to observe that no ear-bones or fragments of other cetacean bones 

 were obtained from the dredgings north of the Equator. The stations south of the 

 Ec[uator, where the bones of Cetacea were found, may be arranged in two groups, the one 

 in comparatively close proximity to continental land, the other in mid-ocean. In the 

 first of these groups the number of ear-bones found in any single station was small, 

 apparently, because, from their proximity to land, and to the influence of the solids 

 suspended in the currents of great rivers, they would become covered over, and imbedded 

 in detritus falling to the bottom of the ocean. Thus only one bone, and that the tymj^anic 

 bulla of a Ziphius, resembling Zijthius cavirostris, was obtained in the South Atlantic 

 at Station 131, oif the east coast of South America. One station (160) south of the 

 Australian continent yielded only a few ear-bones. A station (299) off" the west coast of 

 South America yielded only the tympano-periotic bone of a single species, one of the 

 Delphinidte. Stations 143 and 293 gave only fragments of bone, which could not 

 definitely be pronounced to be cetacean. All the other stations, viz., 274, 276, 281, 285, 

 286, 289, belonged to the second group, and were in the central southern portion of 

 the Pacific Ocean, i.e., in localities the farthest removed from continental land. These, 

 as" Mr Murray has pointed out in his Eeport, are areas of exceedingly slowly accumulating 

 deposits, and consequently in them the bones dredged up at each station were, as a rule, 

 much more numerous than at the stations nearer to the great continents, for they were 

 not imbedded in thick strata of substances which had fallen to the bottom. 



In all tlie localities, except 299, 293, and 143, where merely a single ear-bone or a 

 small fragment of bone was found, the deposit at the bottom of the ocean was, as Mr 

 Murray informs me, a red or chocolate-coloured clay, containing, besides the ear-bones, 

 many hundreds of sharks' teeth and nodules of manganese. The preservation of the ear- 

 bones and of the fragments of the beaks of ziphioid whales is accounted for by the extreme 

 density of these portions of the skeleton. Some of the bones were in a much Ijetter state 

 of preservation than others. In some the manganese coating was extremely thin, and 

 but little had entered into the Haversian canals and lacunse, so that a fractured surface 

 was greyish- white (Mr Murray's PL X. figs, lo, \h, 2a, 4a). Others again were not only 

 thickly encrusted with the mineral, but the Haversian canals and lacunse were infiltrated 

 with it, so that a fractured surface was dark brown or black, and the bones were extremely 

 brittle. The chemical composition of these bones "was thus entirely altered, and this was 

 more especially the case with the fragments of the flat bones, and others of a more porous 

 texture which formed the nuclei of so many of the manganese and iron nodules. It is 

 worthy of note that no bone was identified as belonging to the great sperm whale 

 {Phi/seter macrocephalus) , althaugh the track of the Challenger, at the stations where such 

 large hauls of cetacean bones were dredged up, was through the seas frequented by this 

 huge cetacean; but the tympanic of the short-headed sperm whale [Kogia) was obtained 

 at one station (286). Further, it is to be noted that the bones obtained did not present 



(ZOOL. CHALL. EXP. — PAST IV. — 1880.) D 6 



