A new genus Protoleptoneta (P. bulgarica n. g., n. sp.) is described, which was collected in caves of the Western Balkan mountains - Bulgaria. The new genus unites features of the genera Leptoneta and Paraleptoneta but there are many differences, which divide it from these genera. It differs from Leptoneta as follows: the tarsus of male palp does not possess the characteristic apophysa of Leptoneta; the tarsus is less depressed and does not branch out; the teeth of chelicerae are equable and equidistant. It differs from Paraleptoneta as follows: the femora of male palp is spineless; near the top of tarsus, on ectal side, there is a thicker spot, provided with a strong spine longer than others; the tarsus is more depressed. Paraleptoneta italica is placed in the new genus Protoleptoneta. The origin and relationships between the genera Protoleptoneta, Leptoneta and Paraleptoneta are discussed; a hypothesis is that the genera Leptoneta and Paraleptoneta had been developing as independent phyletic groups and the origin of the two had been Protoleptoneta.