PALAOSPOND YLUS 71 
esses. Its skull was highly evolved: in its anterior part 
were represented, according to Traquair, the palatine car- 
tilages; the brain case was complete, and the auditory 
capsules were of relatively enormous size. The lateral 
plates of the neck region are as yet uninterpretable. 
From the evidence of Palzeospondylus, accordingly, it 
may reasonably be inferred that lamprey-like forms existed 
in highly specialized conditions, even at the beginning of 
Devonian times. If they then existed, it is of course not 
impossible, and perhaps even not improbable, that their 
offshoots may have culminated in the Ostracoderms, as 
Smith Woodward has suggested. These can certainly 
belong to no gnathostome stem. Their organs, though 
often highly specialized, were yet of the most primitive 
order, —lack of paired appendages,* softaess of axial parts, 
lowly sense organs; even the dermal plates, elaborate in 
their subdivision or ornamentation, or in the special uses, 
as “‘opercula,” “ pectoral fins,” or “fin rays,” T are yet but 
primitive specializations of the exoskeleton. 
* The presence of paired fins in Palzeaspis, as determined by Claypole, has 
not been confirmed. The present writer, to whom the type specimens were 
kindly shown by their describer, must regard these structures as elasmo- 
branchian (Chimzroid?) spines, in crushed condition, accidentally associated 
with the head region of the fossil. 
¢ It is obvious that these structures are but analogous to the opercular and 
fin structures of fishes, and would tend to separate, rather than closen, the 
ties of kinship of these groups. 
