370 PROF. ST. GEORGE MIVART ON THE 
PLotus. 
Cervical vertebra 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. Vertebre generally but little swollen or pneu- 
matic; styloid processes short in the more anterior vertebra, but enormous in the eighth, 
and long in the four or five succeeding vertebre ; anterior cervical vertebre very long, 
and increasing in length to the eighth; eighth and tenth vertebre bending dorsad 
from ninth ; hypapophyses present in the first and in from the fifteenth to the twentieth 
vertebre ; in twenty-third to twenty-sixth vertebra a median subcentral process of 
peculiar nature; a complete hemal arch in ninth to fourteenth vertebre ; strong lateral 
ridges on centra of seventeenth to twenty-sixth vertebra, bent down in twenty-second 
to twenty-sixth ; ridges and processes generally rather sharper than in Sula; meta- 
pophyses as sharp as in Phalacrocoraz, 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 vertebr with no hypapophysis, no lateral canal, no interzygapophy- 
sial ridge, and hyperapophyses slightly larger relatively than in Pelecanus; fifth and 
sixth vertebre 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 first 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 hemal arch, with rugged but not very prominent 
metapophyses, and with styloid processes enormously longer than those of seventh 
vertebra, with prezygapophyses 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 vertebre. 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 hemal 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 hemal arch ; the postzygapophyses of the eleventh 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 hemal arch; fourteenth vertebra the last 
with a hemalarch. 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 
