26 



NEW YORK STATE MUSEU^ 



jaws, of a segmented axial skeleton in the trunk, or of arches for the sup- 

 port of paired limbs. Indeed, appendages themselves are confined to a 

 single order, the Antiarcha, where oarlike swimming organs appear to have 

 developed from an integumentary fold on either side of the body, unsup- 

 ported by rays, and in a manner fundamentally different from the fins of 

 typical fishes. It is extreme!)' doubtful whether the jointed pectoral limbs 

 of the Asterolepidae can be regarded in an)' sense as homologous with the 



fins of fishes. 



Within the last decade, our knowledge of the 

 variety, structure and mutual relationships of primi- 

 tive chordates has been vastly increased. Familiar 

 genera have been most assiduousl)' reinvestigated, their 

 occurrence has been detected in fresh localities, and 

 many new forms of the utmost importance and interest 

 have been brought to light. It will suffice to mention 

 here only the classic researches of the late Dr Ramsey 

 H. Traquair on the Old Red sandstone fishes of North 

 Britain, and the beautifull)' preserved Drepanaspis 

 from the Hunsriick slate (Lower Devonic) of Rhenish 

 Prussia ; whereas in this countr)-, the principal advance 

 has been made b)' Professor William Patten, of Dart- 

 mouth College, in his studies of Bothriolepis and the 

 Tremataspidae. 



Amongst other results achieved within recent 

 years, not the least important is the insight which 

 has been gained concerning interrelations and prob- 

 able lines of descent among the different orders 

 of Ostracophores. Reference has already been made 

 line of Ateieaspis t c s s e 1- to the dlscovery of primitive genera which throw a 

 so as to appear in profile (After flood of light upon the affiuitles of Pteraspls and its 

 allies, and enable us to trace them back to an ancestral 



family in which the dermal armor retained its generalized form of shagreen 



