1899.] OSTEOLOGY OF THE TUBINARBS. 405 



Group 0. Supra-orbital grooves deep and wide, sharply defined, and tending 

 to meet in the middle line ; pterygoids rod-shaped, with articular surfaces 

 for the basipterygoid processes — which are often vestigial ; vomer uioi-e or 

 less boat-shaj)ed, not cleft more thau half its length; length of anterior 

 nares never more than ^ that of upper jaw. 



a. Lachrymal free. 



a'. Supero-e.xternal angle of antorbital plate incomplete, forming with the 



lachrymal a large foramen Puffinus. 



Friofinus. 

 Majaqueus, 

 b'. Supero-external angle of antorbital plate complete, closing the space 



between itself and the laeliry mal Bulweria. 



h. Lachrymal anchylosed with nasal. 



c'. Size very large ; basioccipital with well-developed mammillary pro- 

 cesses ; a large space between the dorsal border of the antorbital 

 plate and the frontal; postorbital processes tui'ning downwards and 

 ending in a point; lachrymal with the horizontal grently exceeding 

 the vertical axis ; quadrato-j iigal bar with a strongly marked trianguliir 



process for artifulation with tlie quadrate Ossifmgci. 



d'. Size not exceeding 4 inches ; basioccipital without mammillary pro- 

 cesses ; postorbital processes with a squarely truncate outer border ; 

 lachrymal with the horizontal and vertical axes about equal ; quadrato- 

 jugal bar of uniform thickness throughout. 

 a''. Interorbital region of frontals dividing supra-orbital grooves 

 moderately wide ; lachrymal with its postero-dorsal free edge 

 produced laterally into a pair of conspicuous wings. 

 a^. Vomer tapering anteriorly to a point ; beak stout and wide, not 

 conspicuously narrower at the tip ; anterior palatine vacuity very 

 wide, not bounded by a flattened ledge on either side ; palatines 

 elongated, ventral surface conspicuously keeled posteriorly. 

 a^. Temporal fossa deep, nearly meeting in mid-dorsal line. 



Fiilmarus. 

 b*. Temporal fossa shallow, divided by the roof of a distinct 



cerebellar prominence Daption. 



¥. Anterior end of vomer more or less hidden by the maxillo-palatine 

 processes, which meet in the middle line ; palatines short and 

 broad, proximal end not conspicuously keeled ; anterior palatine 

 vacuity narrow, bounded on either side by a flattened ledge ; beak 

 more or less conspicuously depressed, the extreme form resembling 



that of BalcBiiiceps Prion. 



c^. Vomer terminating anteriorly in a long spine ; palatines elongated ; 

 beak slender, 

 c*. Anterior limb of free bifid end of lachrymal longest ; inter- 

 orbital region of frontals less than width of supra-orbital groove , 



Thalassceca. 



d*. Posterior limb of bifid end of lachrymal longest and directed 



backwards ; interorbital region of frontals much greater thau 



width of supra-orbital grooves (Estrelata. 



b". Supra-orbital grooves divided by a thin bony ridge ... Priocella. 



DlOMEDEID^. 



a. Interorbital region of frontals broad ; antorbital plate not extending out- 

 wards to the level of the outer margin of the lachrymal ; with a well- 

 marked tubercle lying between the mammilary processes. 

 a'. Interorbital region of frontals not exceeding J of the width of the frontals 

 between the lachrymals ; pterygoid ends of the frontals becoming 

 abruptly wider in the region of a line drawn through the median 

 palatine keel Biomedea. 



Proc. Zool. Soc— 1899, No. XXVII. 27 



