Investment bank B. Riley & Co. is the sole underwriter in a secondary offering of 2.85 million shares of stock in Palo Alto-based communications company Ooma Inc.

The bank, owned by parent company B. Riley Financial Inc. of Woodland Hills, will represent entities affiliated with venture capital firm Worldview Technology Partners Inc. of San Jose, which is selling the shares.

The public offering is priced at $8.65 a share, which should raise gross proceeds of approximately $24.6 million to the selling shareholders. Ooma will not receive any money from the transaction.

B. Riley has the option to purchase up to 425,000 additional shares, and the offering is expected to close Jan. 19.