26 



NEW YORK STATE MUSEUM 



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 extremely doubtful whether the jointed pectoral limbs 

 of the Asterolepidae can be regarded in any sense as homologovis 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 assiduously 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 beautifully preserved Drepanaspis 

 from the Hunsruck slate (Lower Devonic) of Rhenish 

 Prussia ; whereas in this country, the principal advance 

 has been made by 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 



Fig. 3 Diagrammatic restored out- i i- /• . . . i • i i 



line of Ateieaspis tessei- to thc Qiscovery of primitivc genera which throw a 



lata Traq., the tailturned round- - ri*i i rr ' ' rr^ * i- 



so as to appear in profile (After uood ot light upoo the aitimties 01 rteraspis 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 



