THE TEETH OF BIRDS. 261 



Merganser. And Geoffrey St. Hilaire had described a series 

 of vascular pulps as existing on the margin of the jaw of 

 parroquets just about to be hatched, which, though destined 

 to form a horny bill, and not to be calcined into teeth, yet 

 strikingly recalled dental pulps. Then there is also the 

 famous fossil Archseopteryx, an anomalous oolitic bird, with 

 a long and jointed tail, which is by many zoologists believed 

 to have possessed teeth. There is a flaw in the evidence, 

 however, inasmuch as the toothed jaw is not in situ, and 

 therefore may possibly have belonged to some other animal 

 than that perpetuated in the rest of the fossil impression, 

 though probability is altogether in favour of its really 

 belonging to the Archseopteryx. 



In successive expeditions, conducted under great difficulties 

 owing to the extremes of heat and cold, and to the hostility 

 of the Indians, the remains of no less than one hundred 

 and fifty different individuals referable to the sub-class 

 ODONTORNITHES have been obtained by Prof. Marsh ; they 

 are classified under nine genera, and twenty species. 



They are referable to two widely different types, one 

 group consisting of comparatively small birds, with great 

 power of flight, and having their teeth implanted in distinct 

 sockets (Odontotorna}, illustrated by the genus Ichthyornis 

 as a type) ; the other group consisting of very large swimming 

 birds, without wings, and having teeth in grooves (Odontolcae, 

 type genus Hesperornis). 



In Ichthyornis the teeth were about twenty-one in number 

 in each ramus, all sharp and pointed, and recurved ; the 

 crowns were coated with enamel, and the front and back 

 edges sharp but not serrated. 



They are implanted in distinct though shallow sockets, 

 and the maxillary teeth are a little larger than those 

 opposing them ; the premaxillaries were probably edentulous, 

 and perhaps covered with a horny bill. 



In the lower jaw the largest teeth occur about the middle 



