AXIAL SKELETON OF THE PELECANID^E. 371 



seventeenth vertebra; postero-external angles of centrum of eighteenth vertebra ex- 

 tensive, and extending more preaxiad than in Phalacrocorax. Nineteenth vertebra with 

 a small hypapophysis ; centrum not at all laterally compressed, but ventrally flattened. 

 Dorsa of tenth to fourteenth vertebrae form a longitudinal groove; great lateral com- 

 pression in centra of twenty-second to twenty-sixth vertebrae ; seventeenth to twenty- 

 first vertebrae flattened beneath ; twenty-second to twenty-fifth vertebrae opisthoccelous ; 

 parapophyses of second sacral vertebra not stronger than those of first ; parapophyses 

 of sacro-caudal vertebrae rather suddenly bent dorsad. Ilio-caudal processes long and 

 pointed ; obturator-foramen shorter and rounder than in the three preceding genera ; 

 sacro-sciatic foramina hidden when the pelvis is viewed dorsally, because of the length 

 of the transverse processes of the sacro-caudal vertebrae, which extend the ilium so 

 much outwards on each side ; transverse diameter of pelvis between its antitrochanteric 

 processes falls short of that of the most preaxial part of the ilia ; lateral acetabular fossae 

 small and triangular ; no supraacetabular fossa ; pelvis rather short ; postaxial half of 

 external margin of ischium strongly convex ; ventral surface of conjoined ischium and 

 ilium rather extensive ; ventral surface of ischium very slightly ridged ; ischium, ex- 

 ternal to obturator-foramen, broad. Pygostyle much laterally compressed and dorso- 

 ventrally curved. All the long vertebral ribs with an uncinate process, except the 

 last rib ; last sternal rib not expanded proximally. Length of sternum exceeding its 

 breadth but little more than in Pelecanus ; lateral xiphoid processes narrow, long, and 

 pointed ; pleurosteon much narrower dor so- ventrally than in Pelecanus and with only 

 four articular surfaces. 



CHARACTERS OF THE PELEOANID^E. 



Cervical vertebrae 15-18, cervico-dorsal 1-3, together 17-20 ; dorsal 5 or 6, prelumbar 

 2226, lumbar 3-5, together 8-10 ; cervical to lumbar inclusive 25-30, lumbo-sacral 

 1-3, lumbar and lumbo-sacral 5-7, sacral 1-3, sacro-caudal 4-8, caudal 5-8, sacral to 

 caudal inclusive but without pygostyle 13-18: total 40-49. Vertebral ribs 6-9; sacral 

 ribs 5-7. A sudden change of form arising in either eighth or ninth vertebra, such 

 vertebra being pressed back postaxiad at its preaxial end, and having both the vertebra 

 in front and behind it bent dorsad from it ; neural arch of seventh or eighth vertebra 

 suddenly deeply concave at its hinder margin, save in Plotus; median hypapophysis 

 always to seventeenth vertebra, and possibly present from fourteenth to twenty- 

 seventh vertebra; always a complete, or nearly complete, hremal arch to two or 

 three vertebrae, and generally complete from tenth to thirteenth vertebras, sometimes 

 from eighth to fourteenth ; metapophyses often long and pointed ; atlas generally 

 with an odontoid foramen, sometimes with an odontoid groove ; neural spine promi- 

 nent in seventh to ninth vertebra: ; postzygapophyses fail to attain the postaxial end 

 of the centrum, for the first time, in from eighth to twelfth vertebrae ; twentieth to 



VOL. x. PART vn. No. 8. August 1st, 1878. 3s 



