On page 414, he starts by mentioning the 4-fold Vinaya classification: male, female, both, neither. Then he cites Zwilling (page 205) as saying the Atharva Veda distinguishes pandakas from males & females, "and implies that they were transvestites". The grammar of Harvey's sentence doesn't make clear whether it was the AV or Zwilling that was doing the implying. Harvey goes on to report Buddhaghosa as saying both pandakas & hermaphrodites are determined from conception. He continues citing Buddhaghosa as listing 5 types of pandaka: 

 #one who fellates a man 
 #a voyeur 
 #one who ejaculates by some means (unspecified) 
 #one who, through karma, is a pandaka only 1/2 the month 
 #non-male