17,18,19

17- the three purses that the beast has contain a lion, a goose, and a pregnant sow. These could represent the sins which are in the eight level. The lion is representative of god, of power, and of pride. The goose is a symbol of anger or of greed as in the "golden goose" the pregnant sow could be a symbol of lust. The eight level of hell is reserved for the fraudulant. so I'm not sure how these relate. Perhaps these three animals are follow-ups to the three animals which dante was following in the beginning of the story. The wolf, leopard, and the other animal which represent the sins.
18- "isle of Lemnos after the time when its bold, pitiless women killed every male; the women of the isle of lemnos were disrespectful to aphrodite so she cursed the women to be foul smelling until their husbands turned to concubines. So the women of the island killed their husbands and formed acolongy. Jason then came and had a child with the queen of the island.
19- "a son who truly came out of the she-bear"the bear is a symbol of power strength and in some cultures, royalty. this could be an allusion to the tales of the berserkers who transformed into bears or the tale of rolf krokki which contained many half man and half bears. however Dante was italian and those stories were from northern Europe so any connection is not likely.