18y9.J oSTEOLoeY or ihb iubinaues. 409 



A. Humerus non-pneumatic ; crista inferior never inflated along its free edge. 



PfocellariidcB. 



B. Humerus pneumatic; crista inferior inflated along its preaxial border; 



sub-trochanteric fossa small, receiving several pneumatic foramina. 



Dioiucdeidce, 



F. Pelyio Limb. 



All the bones non-pneumatic ; tibio-tarsus with a greatly enlarged ecto- 

 cnemial crest tbriuing a large flabelliform crest rising high above the articular 

 surface ; with an extensor bridge ; outer and middle toes of equal length ; 

 hallux more or less vestigial ; tibio-tarsus with a more or less well-mai'ked 

 intercotylar tubercle; 1st phalanx of D. II. = to or longer than that of D. III. 



A. Hjpotarsus complex Proceilariide. 



a. Tarso-uietatarsus longer than the outer toe. 



a'. Ungual phalanges flattened ; basal phalanx of middle toe as long as or 

 longer than next two taken together {Forbes). 

 a". Tarso-metatarsus markedly longer than the outer toe, grooved an- 

 teriorly throughout, its length = ^ that of the tibio-tarsus ; ph. 1 



of D. II. longer than ph. 1, D. III. & IV Cymodroma. 



b". Tarso-metalarsus uiueh longer than outer toe ; trochlea all in same 

 plane; grooved anteriorly, much flattened distally antero-pos- 

 teriorly ; 3 toes nearly = ph. 1, D. II. & III., = longer than IV. 



Fregctta, 



c". Tarso-metatarsus longer than outer toe, | as long as tibio-tarsus ; 



fibular ridge scarcely longer than the width across the proximal 



articular surface of the tibio-tarsus ; basal phalanges of D. II. and 



III. = and longer than that of IV Oceanites. 



d". Tarso-metatarsus much longer than the outer toe, J as long as tibio- 

 tarsus, with a shallow groove throughout its whole length ; basal 

 phalanges D. II. and Ill.^and longer than IV. ; outer and middle 



toes equal Pelagodroina. 



b'. Ungual phalanges pointed ; basal phalanx of middle toe shorter than 

 next two joints (Forbes). 



e". Tarso-metatarsus only slightly longer than the outer toe; fibular 

 ridge obsolete Procellaria. 



b. Tarso-metatarsus shorter than outer toe, but much longer than femur. 

 c'. Fibular ridge obsolescent. 



/". Tarso-metatarsus faintly grooved anteriorly, its outer border raised 



into a sharp ridge Puffinus. 



g". Tarso-metatarsus deeply grooved anteriorly, outer border not con- 

 spicuously develoi^ed Bulwena. 



d'. Fibular ridge distinct. 



h". Tarso-metatarsal groove nearly obsolete f Daption, 



\ Prion. 

 i'\ Tarso-metatarsus grooved anteriorly and posteriorly ... (Estrelata. 



a!'. Groove deeper, length not exceeding 2| in Majaqueus, 



i^. Groove shallower, length not less thau'Sf in Osdfraga. 



c. Tarso-metatarsus shorter than outer toe, scarcely longer than femur. 



k". Tarso-metatarsal groove obsolescent, hallux present. 



a^. Ectocnemial crest stronger; shaft of tibio-tarsus not exceeding 



^2 ^^ ThalasscEca. 



d^. Ectocnemial crest weaker ; shaft of tibio-tarsus not exceeding 



<^i i" Pnocella. 



I". Tarso-metatarsal groove obsolescent ; hallux absent .. . Pelecanoides. 



B. Hypotarsus simple ; ectocnemial large, forming an acute angle with the 



entoonemial crest proximally ; fibular ridge scarcely raised above half of 



S"*^'' Ucomedeidce^ 



