This image shows a number of characters mentioned in the descriptions of Bigot and Brimley (see info page).

Perhaps most conspicuous are the bright white-pollinose post-orbital stripes. Note that they are not connected across the hind edge of the vertex to form a "distinct uninterrupted post-vertical stripe", as they would be in P. excisus and P. townsendi (cf. pg. 171 of Camras (1955))...and sometimes also in P. bulbirostris from specimens ID'd by Camras that I examined yesterday at the Essig Museum.

Note also that the callosity at the vertex is mostly yellowish-brown (continuing a bit down the back of the head), while the upper portion of the occiput is black, and the lower portion whitish.

The scutellum is black; the anterior half of the post-scutellum is covered by a more-or-less continuous pollinose white stripe which continues down the side of the thorax, in front of the halter, to the pleurotergite; and there are white pollinose dash-like markings on the humeri, and small such spots above the wing bases. Note also the mostly reddish hind femora...the character in the terminal couplet of Camras' key for P. nigrimanus. Note, finally, the largely black abdomen, with the yellowish band at the junction of the 2nd and 3rd segment, and yellowish-pollinose dustings apically on the distal tergites.