320 



EDWIN S. GOODiaOH. 



even larger size ? During this important cliauge what has 

 become of the muscles attached to the girdle for the moving 

 ot" the fin? Have they disappeared also^ and been replaced 

 by others, or have they shifted their base of attachment on 

 to the basals ? What evidence is there that the moveable 

 jointj where the base of the fin skeleton articnlates with 

 the girdle, firmly embedded in the body -wall, has not always 

 been where it now is, but has been carried forwards at the 

 tip of the basal bones and lost its primitive function ? What 

 evidence is there that this primary articulation between the 

 moveable fin skeleton and the fixed pelvic girdle, has been 



Fig. J. — Ventral view of Uie pelvic girdle and fins of Gad us morrliua, L. 



replaced by a new joint between two different regions of the 

 fin skeleton itself ? 



Moreover, is it credible that such a fundamental alteration 

 iu the relations of the internal skeleton should have taken 

 place without a corresponding change iu external shape ? 

 Here the evidence afforded by the structure of Eusthenop- 

 teron may be called in. On the one hand there seems to be 

 no reasonable doubt that the pelvic bones of this fish are 

 homologous with those (so-called basals) of Polypterus, 

 Coelacanthus, or Amia (Figs. G, L, and H) . On the other hand, 

 it will, I think, be allowed that the moveable joint whereby 



