1899.] OSTEOLOGY OF THE PYGOPODES. 1043 



Group i. (Type P. JluviatUis.) Temporal fossa ill-defiued; cerebral pro- 

 minence small ; fossa for insertion of temporalis muscle not deeply 

 excavated on postorbital region of frontals ; with a small postorbital 

 process ; upper jaw not longer than cranium. 



Podicipes. 



B. With abroad bifid, overhanging postorbital process Mchmofphorus. 



B. Yeb.tebe.5:. 



Emargination of neural arches of cervical vertebra caudad, slight, never 

 extending forward beyond the level of the postzygapophyses ; anterior cervical 

 ribs of great length ; all cervieals save atlas and axis with a bony vertebrarterial 

 canal closed externally by the cervical ribs ; synsacrum elongated, and laterally 

 compressed, so as to be almost styliform. 



A. Neural spines of anterior cervieals in form of long median ridge; hypera- 



pophyses of anterior cervieals widely separated ; neural arch of 2nd, 3rd, 

 and 4th with a rounded free posterior border. All thoracic vertebra; free, 

 the lst-3rd with long _L-shaped hypapophyses ; 6 free caudals, excluding 

 the pygostyle ; pj'gostyle broad and strong Colyjibidj:. 



B. Neural spines of anterior cervieals almost obsolete ; catapophyses of anterior 



cervieals meeting in the middle line ; last cervico-thoracic and thoracic 

 1-4 anchylosed ; free end of hypapophyses scarcely, if at all, laterally 

 expanded ; 7 free caudals, excluding pygostyle ; pygostyle feeble. 



PODICIPEDID.E. 



It is almost impossible to distinguish, in the synsacrum, lumbar, lumbo- 

 sacral, and sacral vertebrae. The lumbar region has apparently undergone a 

 great shortening. There are no vertebrae which can be distinguished— in the 

 dried skeleton — as sacral. The postsynsacral region— that lying behind the 

 acetabulum— is of great length. 



The vertebral formula must therefore stand as follows: — 



Syn. sc. 



Cv. 13. Cv. th. 1. Th. 6-1-2. L. Lb. sc. Sc.?5. Cd. 10+7=44. 



^8 17 



Colynd)id(B. 

 Syn. sc. 



Cv.20. Cv.th.2. Th.6+1. L. 4. Lb.sc.3. Sc.2. Cd. 6-1-7=51. 



Podinpedide. 



C. Steenum and Pectoeal Giedle. 



Corpus sterui with a pair of notche.s posteriorly ; coracoid grooves deep ; 

 metasternum either notched posteriorly, or broadly linguiform, and projecting 

 far beyond posterior lateral processes ; anterior lateral processes not projecting 

 forwards beyond the level of the coracoid grooves ; no supracoracoid foramen ; 

 clavicle not articulating by a glenoid surlace with acromion of scapula. 



A. Greatest width of sternum across anterior lateral processes rather less than 

 \ the length ; coracoid groove moderately deep ; spina externa sessile and 

 bifid ; keel very shallow ; metasternum linguiform, projecting far beyond 

 level of posterior lateral processes ; precoracoid very small ; posterior lateral 

 processes of coracoid large and spinose Colymbid^. 



