No. 377.1 AMIOID AND LEPISOSTEOID FISHES. 349 
on therescould have been no passage across from the one to the 
other. Mr. Woodward’s groups appear to be based on characters 
which are rather degrees in the development of the vertebral 
rings; and, indeed, Amia, a protospondylous fish, would, accord- 
ing to the definitions given, belong to the Aetheospondyli had 
the fusion of “ pleurocentra ” and “hypocentra ” been carried 
out a little further in the tail. 
In both of the groups proposed there are genera in which, so 
far as we now know them, the tendencies of the vertebral 
elements had as yet hardly made themselves manifest. The 
Lepisosteoid series has, in its vertebral structures, remained 
closer to the primitive condition; and its members are, there- 
fore, rather more “ protospondylous”’ than those of the other 
group. 
It may be permitted me in conclusion to correct an unfortu- 
nate error that I made in a paper contributed to the American 
Naturalist, vol. xxxi, p. 402, 1897. I there stated that the 
arches, neural and hemal, originate at a later period in the 
development of the young fish than do the intercalated carti- 
lages. They are developed earlier, and the error was due to a 
slip of the pen. 
U.S. NAT. MUSEUM, 
March 22, 1898. 
