BIRDS WITH TEETH. 



27 



Sub-Class IIT. — ODOxTOHOLCiE. 



Ordek I. — DROMyEOPAPPI. 



Contemporaneous with the Ic/it/ii/oniis, other toothed birds of quite different aspect 

 and characters inhabited the same cretaceous sea which then covered the central and 

 western j)arts of our continent. The former went hovering over the watei-s, dartiii,', 

 like the terns and gulls of the present day, upon the unfortunate fishes which came 

 too near the surface; while the type of the present sub-class, the Hesperornis, or 'the 

 western bird,' as that name literally means, followed the prey to the very bottom of 

 the sea, in diving power and speed surpassing any other bird, living or fossil, and even 

 more fitted for aquatic life than the i)enguin, as it had no wings whatsoever, and its 

 feet were so specially modified for propelling their large bodies through the water that 

 they could hardly move on land. We will further on have ()j)portunity of characterizing 

 the jtenguins as the seals among the birds : Jlcsjierornis and its allies rejjresent the 

 dolphins. 



It is most fortunate for science. Professor Marsh remarks, that Ilesperornis reffulis 

 — with the exception of Arc/iceopteri/.v and LuojHery.i; the oldest bird known — should 

 now be represented by remains as complete as any fossil skeleton yet discovered, even 

 in the later formations, as nearly all the bones of the specimens obtained, when first 

 found in the matrix, were almost as perfect as in life; and the various remains belong- 

 ing to about fifty different individuals of HesjKrornis are now in the museum of Yale 

 College. 



With a general superficial resemblance to that of a loon, the skull of ITesperoniis, 

 in its more important characters, ap]nT)aches that of the Struthious birds, being like 

 the latter dromaaognathous, and having, like them and Ic/tt/ii/ornis, only one facet on 

 the articular head of the quadrate bone. The nostrils are 

 holorhinnl. The brain-case is small, and its sutures entirely 

 fused together. As in Iclitliijornis and many recent water- 

 birds, well-marked glandular depressions extend along the roof 

 of the orbits. The ])reinaxillaries were elongated, forming a 

 long, pointed beak, which in front of the nostrils was a]i])arently 

 covered with a horny sheath, as in modern birds. There were 

 no teeth in these bones, as in the upper jaw they were con- 

 fined to the maxillary bones, which wore armed with (in If. 

 nrjiili.-i fourteen) teeth set in a deep, continuous groove, with 

 oidy faint indications of separate sockets. The lower jaw was 

 thickly set with teeth to the end (in rer/alis tliirty-three), and 

 the two halves were separate, as in Trlitlnjoriiii^, only \mited in 

 front by ligament. The teeth, which are so reptilian in tiieir 

 characters that nobody would hesitate to refer tlicm to that 

 class, had tliey been found alone, were gradually replaced by 

 successional teetli, the germ of the young tooth growing in a 

 pit made in the old one by absorption, thus undermining and 

 at last expelling the latter (Fig. 13). 



In strange contrast to Tr/ii/ii/onii.-i, the present group of fossil birds had vertebra- 

 resembling in their more imjiortant characters the corresponding vertebrie of existing 



Flii. 1.!. — T....lli .if //../"•'•- 



orniji, flilnr;:''*!; c, germ of 



6«cunil looth. 



