260 A MANUAL OF DENTAL ANATOMY. 



10 to 15 inches in total length of body. In the Pterodactyls 

 the jaws are furnished with long, slender, sharp teeth in 

 their whole length : but in Ramphorhynchus the anterior 

 extremities of the jaws are without teeth, and it has been con- 

 jectured that these portions were sheathed in horny beaks. 



And Prof. Marsh (American Journal of Science, 1876,) has 

 discovered, in the same formation in which he found the 

 toothed birds, several species of Pterodactyls wholly without 

 teeth, for which the generic name Pteranodon is proposed. 



The jaws, which are more like those of birds than those of 

 any known reptile, show no traces of teeth, and the pre- 

 maxillaries seem to have been encased in a horny covering. 



THE TEETH OF BIRDS. 



Prior to the discovery by Professor Marsh of Yale College, 

 in 1870, of the remains of birds with teeth in the cretaceous 

 formations of Western Kansas, little was with certainty 

 known about the existence of teeth in any bird, although 

 one or two fossils, leading to the suspicion that birds might 

 have possessed teeth, were known. The state of knowledge 

 up to that time has been clearly summarised by Mr. Wood- 

 ward (Popular Science Review, 1875,) to this effect : that 

 it had been long supposed that no examples of teeth were to 

 be met with amongst the birds, although some, such as the 

 Merganser, have the margins of the bill serrated, so that the 

 functions of teeth are discharged by this horny armature of 

 the jaws. 



It is noteworthy that the margin of the bone of the jaws 

 is also serrated, each serration corresponding to a similar 

 serration in the bill. In the fossil bird described by Pro- 

 fessor Owen, from the London clay, under the name of 

 Odontopteryx toliapicus, the form of the bill is not known, 

 but the margins of the jaws are furnished with strong bony 

 prominences, far more conspicuous than those of the 



