THE MYRIAPODA OF NORTH AMERICA. 143 



Opixtlinitr<i Wood has principally been used in place o f 

 because Newport based liis genus upon ail erroneous chii'/aeter the 

 possession ol' an ocellus. Lu his description of Theatops, Newport 

 says: "O.-rUi ilixttHoti"; while in the description of its species, he says: 

 "Ocelli* itii-oitxpii-iiix, IdfcrtilihiiH." In these two statements Newport 

 seems to contradict himself and to be uncertain about the possession 

 of an ocellus. Probably Newport has mistaken an accumulation of 

 pigment for an ocellus, and his observations as to the possession of an 

 ocellus are erroneous, at any rate. Say did not see a trace of an ocellus 

 in the same specimens. 



The supposition that Newport has made an erroneous observation is 

 further strengthened by the fact that the possession of an ocellus is 

 the only difference between Tlirttlopx and Ojii^tltciitci/a. Notwithstand- 

 ing this erroneous derivations of Theatopx, it must be used in place of 

 Opisthemega. 



!'!. .Moxops. 



1847. 3Io>i<tp.f ( ;<Tvais. Apti-n-s, iv, '-'91 (Cri/i>tpx nlyru Newport). 



This name was first used by Billb. in 1820, as a genus of Crustacea, 

 and Monops (Jervais must give place to another. 



:!(>. RHYSIDA. 



IMt. UrancliinxhniHt Nc\vj>ort. Trans. Liiin. Soc., 411 (litholiodes). 

 1863. Khysithi Wood. .loam. Phihi. Acatl. Nat. Sci., -10. 



As I>i-<nichinxt<nna Newport is ])reoccupied by a genus of fishes, Dr. 

 Wood has proposed the name Rhyxiila as a substitute, which we are 

 compelled to use in place of 



1844. Heturostoma Newport. Trans. Linn. Soc., 275 (lrii/<ijnHla.) 

 1847. J facet urn Koch. Syst. Myr., 77 fc 171 (capense). 



Because Hettrostonia Newport is preoccupied (Heterostoma Hart- 

 niann, Moll., IStM) we must use, its synonym, Dacetiim -Koch, instead. 

 INDIANA UNIVERSITY, June I, 1888. 



