Two simple questions about microRNA's name - (Jul/21/2006 )

I want to ask two simple questions about microRNA's name:

1). When I use the microRNAs database on Sanger, I found some microRNA's annotation in the item of 'Evidence' is 'by similarity'. What does that mean?
http://microrna.sanger.ac.uk/cgi-bin/seque...l?acc=MI0000300
2).I have searched some microRNAs that can hit one rat gene. According to some papers, I got several candidate microRNAs. So is it right to say that rno-miR-xx is better than hsa-miR-xx just because the former microRNA belongs to the same species of target gene?

1) If you click on that link 'by similiarity' it shows an experimentally verified mature miRNA sequence for dre-mir-223. The 'Evidence' that hsa-mir-223 is real is its sequence similarity to the dre-mir-223. hsa-mir-223 has not been directly pulled amplified and sequenced.

2) A rat-mir and the hsa-mir can be the same miRNA. In other words miRNA can be 'expressed' accross different species. For example there are some found in human, mouse and rat. They will have different transcription levels depending on species for a myriad of reasons. This is true for different tissues within the same species as well.