THE REGION OF THE SPINAL CORD AI5 
rather a free pleuron, which has been easily pushed at an angle to 
the body-skeleton in the process of fossilization. Patten thinks that 
this fringed appearance is evidence of a number of segmental appen- 
dages which were jointed to the corresponding body-segments, and in 
the best specimen at the South Kensington Natural History Museum 
he thinks such joints are clearly visible. He concludes, therefore, 
Fic. 161.—A, Facsimine or Woopwarp’s DrawinG OF A SPECIMEN OF Cephalaspis 
Murchisoni, 48 SEEN FROM THE sIDE. THE CEPHALIC SHIELD IS ON THE 
RIGHT AND CAUDAL TO IT THE PLEURAL FRINGES ARE WELL sHowN; B, 
ANOTHER SPECIMEN oF Cephalaspis Murchisoni TAKEN FROM THE SAME BLOCK 
OF STONE, SHOWING THE DERMOSEPTAL SKELETON AND IN ONE PLACE THE 
PuevRAL FrRinazs, be. 
that the cephalaspids were arthropods, and not vertebrates. I have 
also carefully examined this specimen, and do not consider that what 
is seen resembles the joint of an arthropod appendage; the appear- 
ance is rather such as would be produced if the line of attachment of 
Patten’s appendages to the body were the place where the pleural 
body folds became free from the body, and so with any pressure a 
