In this report emphasis is placed on the dorsal skull characters of the genus Spea and the three species, bombifrons, hammondii, and intermontana. Spea hammondii is a polytypic species with at least three subspecies, hammondii, multiplicatus, and stagnalis, each of which is described and the distribution indicated. Drawings and photographs of skulls are provided for each species, with hammondii and intermontana receiving special consideration.
Tanner, Wilmer W.
"Status of Spea stagnalis Cope (1875), Spea intermontanus Cope (1889), and a systematic review of Spea hammondii Baird (1839) (Amphibia: Anura),"
Great Basin Naturalist: Vol. 49
, Article 5.
Available at: http://scholarsarchive.byu.edu/gbn/vol49/iss4/5