ARP Setup Inquiry

I am trying to set up a static arp entry (easy just arp -s ip mac) however when I ad this static arp entry it does not replace the old entry. So I have 2 mac addresses for the same ip.

arp -a returns the following (I xx out the unimportant arp entries)

--> ? (192.168.1.1) at 90:72:40:b:dc:a1 on en0 permanent [ethernet]

--> ? (192.168.1.1) at 8c:e2:da:f0:33:15 on en0 ifscope [ethernet] (I want to completely remove this entry)

? (192.168.1.62) at xx:xx:xx:xx:xx:xx on en0 ifscope [ethernet]

? (192.168.1.68) at xx:xx:xx:xx:xx:xx on en0 ifscope [ethernet]

? (224.0.0.251) at xx:xx:xx:xx:xx:xx on en0 ifscope permanent [ethernet]

On windows I am able to use the netsh command to accomplish this. Any suggestions?