370 PEOF. ST. GEORGE MIVART ON THE 



Plotus. 



Cervical vertebrae 18, cervico-dorsal 2, together 20; dorsal 5 or 6, lumbar 4, lumbo- 

 sacral 2 or 3, sacral 2, sacro-caudal 4 ; caudal, without pygostyle, 7 or 8 : total 45 or 46. 

 Vertebral ribs 7 or 8, sternal ribs 6. Vertebrae generally but little swollen or pneu- 

 matic ; styloid processes short in the more anterior vertebrae, but enormous in the eighth, 

 and long in the four or five succeeding vertebrae ; anterior cervical vertebrae very long, 

 and increasing in length to the eighth ; eighth and tenth vertebrae bending dorsad 

 from ninth ; hypapophyses present in the first and in from the fifteenth to the twentieth 

 vertebrae; in twenty-third to twenty-sixth vertebrae a median subcentral process of 

 peculiar nature ; a complete haemal arch in ninth to fourteenth vertebrae ; strong lateral 

 ridges on centra of seventeenth to twenty-sixth vertebrae, bent down in twenty-second 

 to twenty-sixth ; ridges and processes generally rather sharper than in Sula ; meta- 

 pophyses as sharp as in Phalacrocorax, but smaller. Atlas with a very small 

 odontoid process and one median hypapophysis ; axis with the merest rudiment of a 

 hypapophysis, small hyperapophyses, and no lateral foramen leading into centrum ; 

 third and fourth vertebrae with no hypapophysis, no lateral canal, no interzygapophy- 

 sial ridge, and hyperapophyses slightly larger relatively than in Pelecanus; fifth and 

 sixth vertebrae medianly grooved beneath ; postzygapophyses of seventh vertebra not 

 more postaxiad than in the sixth ; postaxial margin of neural arch of seventh vertebra 

 not concave, this concavity fixst appearing in the eighth, and there very, slight ; eighth 

 vertebra not pressed back preaxially (the ninth the first to be so pressed back), half as 

 long again as seventh, with no haemal arch, with rugged but not veiy prominent 

 metapophyses, and with styloid processes enormously longer than those of seventh 

 vertebra, with praezygapophyses much more preaxiad than centrum, and with post- 

 zygapophyses not quite so postaxiad as centrum, but very much less postaxiad than in 

 seventh vertebra ; neural spine prominent in seventh and eighth vertebrae. Ninth 

 vertebra pressed back to an enormous degree ; it is thus parallel to the eighth of Pele- 

 canus ; its neural spine not so much developed as that of eighth ; ninth vertebra with 

 a haemal arch, and the first to have one; its hyperapophyses two lateral sharp pro- 

 cesses, which may be so continued as to form a dorsal arch on each side of the vertebra, 

 or else they help to give attachment to such a fibrous arch ; the metapophyses mere 

 ridges ; tenth vertebra with a haemal arch ; the postzygapophyses of the ele^'enth vertebra 

 do not quite reach the postaxial end of the centrum ; but they do not fail to do so for 

 the first time, because they so fail in the eighth (though not in the tenth) vertebra ; 

 postzygapophyses of twelfth vertebra fail very decidedly to reach the postaxial end 

 of the centrum ; thirteenth vertebra with a haemal arch ; fourteenth vertebra the last 

 with a haemal arch. A large, median, plate-like hypapophysis suddenly appears in the 

 fifteenth vertebra, and is still larger in the sixteenth ; it is small and postaxial in the 



