Becent Literature. 235 



what he has here to offer, we are at length presented with the complete 

 result of his patient and faithful investigations, together with the final 

 conclusions deduced from his study of these marvellous forms of bird life. 

 It is safe to say, that no single memoir on fossil birds hitherto published 

 can be compared with this in accuracy of detail, in importance of the 

 material upon which it is based, in beauty of illustration, and in value of 

 results attained. 



Remains of Mesozoic Birds hitherto brought to light have been for the 

 most part too fragmentary and too few to throw much light on the orni- 

 thology of that period. Excepting the well-preserved remains of three 

 individuals of the Jurassic Archcenpteryx, the only other Mesozoic Birds of 

 the Old World are from the Cretaceous of England. The present volume 

 is based on the remains of more than one hundred different individuals of 

 the Odontornithes procured in the Cretaceous deposits of the West during 

 the last ten years. The extent of such remarkably well preserved ma- 

 terial is wholly unparalleled. Since the first fossil bird was discovered by 

 Prof. Marsh, in December, 1870, near the Smoky Hill River in Western 

 Kansas, in middle Cretaceous strata, corresponding to those named by 

 him the " Pteranodon beds," these deposits have yielded nine genera 

 and twenty species, represented by the remains of about one hundred and 

 fifly individuals. Says Professor Marsh, in his Introduction : — 



" A study of this extensive series of Bird remains brings to light the 

 existence in this class of two widely separated types, which lived together 

 during the Cretaceous period, in the same region, and yet differed more 

 from each other than do any two recent birds. Both of these types possessed 

 teeth, a character hitherto unknown in the class of Birds, and hence they 

 have been placed by the writer in a separate sub-class, the Odontornithes. 

 One of these groups includes very large swimming birds, without wings, 

 and with the teeth in grooves (Odontolcce), and is represented by the genus 

 Hesperornis. The other contains small birds, endowed Avith great powers 

 of flight, and having teeth in sockets (Odontotormce) , and biconcave verte- 

 brae ; a type best illustrated by the genus Ichthyornis. Other characters, 

 scarcely less important, appear in each group, and we have thus a vivid 

 picture of two primitive forms of bird structure, as unexpected as they 

 are suggestive." 



These two groups, Odontolcce and Odontotormce, Professor ]\Iarsh com- 

 pares with the Jurassic Saururce of Haeckel, making of the three as many 

 orders of his sub-class Odontornithes. Their characters are contrasted on 

 page 187, and it is interesting to observe, in the tabulation of their charac- 

 ters, how much better known are the Odontolcce and Odontotorma than the 

 much longer known Saururce. 



The work of Professor Marsh, as a whole, is an vinmeasured advance 

 upon all previously obtained knowledge of Cretaceous birds. 



The present volume is divided into two parts, the first treating of Hes- 

 perornis, the second of Ichthyornis and Apatornis, the entire skeletons of 



