By Rishab Shaju and Prakhar SrivastavaJuly 30 (Reuters) - Coinbase Global posted a third straight quarterly loss on Thursday as a prolonged downturn in cryptocurrency markets ‌dented its trading volumes, sending the digital-asset exchange's shares 5.3% lower after the ‌bell. Coinbase's transaction revenue dropped 21% to $599 million during the quarter, from $764 million a year earlier. "Tokenized equities and perpetual futures could offset spot crypto trading volumes, but Coinbase ⁠is behind on both." Robinhood Markets, a much smaller firm in terms of the number of token offerings, also reported a 38% slump in second-quarter crypto transaction revenue, suggesting softer trading volumes across ​the ​market. Without a crypto market turnaround, Coinbase would hope ​for accelerated adoption of stablecoins, Zuller ‌said.