SSH to a device that connects to the internet via shared LAN
Yes, this is possible. It depends on the network addresses you assigned the mac and the Raspberry Pi. For example, if your mac has one interface (en0) on one IP range and the other interface (en1) on another, you can log in via the connection (either en0 or en1) that is on an accessible network. 

In my case, I can reach my home computer via a port forward from the internet. This is done by using a router that allows me to forward specific ports to specific internal IP addresses. 

 -> (port 22 ssh) -> &lt;172.16.0.5:22> 

So, once I'm on my internal machine &lt;172.16.0.5> I can then ssh to a machine connected to my machine via the en1 (wireless network) say 192.168.0.5

So, if you set up a connection from your mac to your raspberry pi on a private network, you can just ssh to your main machine and then to the private ip.