38 Journal of Entomology and Zoology 
It is hardly possible, as I have pointed out, to formulate a gen- 
eral system of the group but among the groups examined the 
Ophiolepidae and the Ophiocomidae are noticeably separate and, 
containing few local genera of well marked characters can readily 
be separated both among themselves and from other families. Be- 
tween the families Ophiothricidae and Amphiuridae I have found 
many points of contact as I did also between some Ophiodermatidae 
and the Amphiuridae. Beyond these generalizations I do not care 
to advance any opinion. 
Following are my results upon those species examined. Ex- 
tremes of measurement and a few notes on certain of the more 
obvious structural details are given. Other details can be made out 
from study of the plates. 
Ophiocryptus maculosus Clark. The smallest specimen meas- 
ured had its disc one mm. in diameter and with arms one and a half 
mm. long. Young of this species differ from adults in few skeletal 
details. The buccal fissures seem less marked and the arms rela- 
tively longer in proportion to the disc. 
Ophioderma panamensis Lutkin. The smallest specimen 
measured two mm. across the disc and with arms eight mm. long. 
Juveniles of this species resemble adults in many points but they 
differ in others. The disc is set well apart from the arms. The 
characteristic notches between the arms in the adults are absent. 
The radial shields are scarcely marked. The branchial spines are 
set almost at right angles to the arms. Not figured. 
Ophioplocus esmarki Lyman. The smallest specimen meas- 
ured was one mm. across the disc and with arms eight mm. long. 
Juveniles of O. esmarki are always distinguishable by pinkish 
bands crossing the arms. This species is especially interesting on 
account of the schizogony that young specimens undergo. 
Amphiodia barbarae Lyman. The disc of the smallest speci- 
men measured was three mm. and the arms twenty-eight mm. long. 
These are always to be distinguished by the exceedingly long arms 
at least ten times the diameter of the disc. Young seem to bear 
many points in common with O. panamansis. 
Ophioneris annulata Le Conte. Specimens of this species vary 
from about one half mm. to two mm. in diameter. They undergo 
schizogony in an unequal plane in certain cases. Like the adults 
the arms have three flattened arm-spines and with banded arms. 
Ophiopteris papillosa Lyman. Measurements of the smallest 
specimen in this species found were for the disc three mm. and for 
the arms tenmm. These are distinguishable by the flat upper arm- 
plates and coarse arm-spines, but these are both characters that 
vary even in one specimen. 
Ophiothria spiculata Le Conte. I found but few specimens of 
this although the adults are abundant. The smallest specimen 
measured one mm. in diameter. The reduction in the comparative 
