-tre·ma
\.ˈtrēmə\  noun combining form 
Etymology: New Latin -tremat-, -trema, from Greek trēmat-, trēma hole — more at throw 
1. plural -tremas\-məz\  or -trema·ta \-məd.ə, -mətə\   : hole : orifice : opening 
< helicotrema >
2. : creature having (such) an opening  — in generic names
< Eurytrema >
1. plural -tremas
< helicotrema >
2.
< Eurytrema >