38 Journnl of Kntomolony and Zoology 



It is hardly possible, as I have pointed out, to formulate a gen- 

 eral system of the group hut among the groups examined the 

 Opiiioh'pidac and the Opliiocfimidai 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 Opiiinfliricidac and Amphiuridae I have found 

 many points of contact as I did also between some Ophiadcrmatidae 

 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. 



Opiiiocnjptiis maridnsii^ Clark. The smallest si)ecimen 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. 



Ophiodcrma panamen-i < 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 

 di'T(M- 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 fi'Jrured. 



Ophioplocus esmarki Lyman. The smallest spei-imen meas- 

 ured was one mm. across the disc and with arms eight mm. long. 

 Juveniles of 0. 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 harharae 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. panamayi-iis. 



Ophioiieris avmdafa Le Conte. Specimens of this species vary 

 from about one half mm. to two mm. in diameter. They undergo 

 schizogony in an unc(|ual jilane in certain cases. Like the adults 

 the arms have three flattened arm-spii'cs and with banded arms. 



Ophi(ipt( ris pajiillosd Lyman. Measurements of the smallest 

 specimen in this species found were for the disc three mm. and for 

 the arms ten mm. These are distinguishable by the flat upper arm- 

 plates and coarse arm-spines, but thc^e are both characters that 

 vary even in one specimen. 



Ophiothrix spicidata he Conte. I found liut few specimens of 

 this although the adults are abundant. The smallest specimen 

 measured one mm. in diameter. The reduction in the comparative 



