To add Ethernet to medusa, which is based on arduino, you maybe able to use the ENC28 module but you will waste most of the resources on the TCP/IP stack.
Good thing dfrobot has this module which uses a chipset with built in TCP/IP stack
I did some googleing for the drivers and there seem to be a lot of info on the web.
Do to forget, for WiFi we recommend this one today
https://www.ghielectronics.com/catalog/product/444
Enjoy