I made up that plural of phallus, and was waiting for one of our scholars to expose the error. When none did, I decided to do it myself. I get a chuckle out of what I found:
Main Entry: phal·lus
Pronunciation: 'fa-l&s
Function: noun
Inflected Form(s): plural phal·li /'fa-"lI, -"lE/; or phal·lus·es
Etymology: Latin, from Greek phallos penis, representation of the penis;
probably akin to Latin flare to blow -- more at BLOW
Date: circa 1613
1 : a symbol or representation of the penis
Phallacies can turn out to be amusing.
