Costacopluma squiresi sp. nov.

(Fig. 1)

Costacopluma squiresi Nyborg, Vega & Filkorn, 2009: 205–207, fig. 2.

Type material. HOLOTYPE: LACMIP 13560, nearly complete carapace with right cheliped preserved, carapace length 11.2 mm, width 11.5 mm, collected from LACMIP locality 11688, Santa Susana Formation, Quarry Canyon, near head of Quarry Canyon, Southern California . PARATYPE: LACMIP 13561, length about 13.0 mm, width 15.8 mm, dorsal carapace and portions of thoracic sternum, collected from LACMIP locality 21580, San Francisquito Formation, about 3.5 km northwest of Warm Springs Mountain, Southern California .

Diagnosis. Carapace small, subtrapezoidal to subhexagonal elongated, widest at posterior one-fourth of carapace; marginal notch separating anterolateral from lateral margins; transverse ridges moderately strong, with sharp, granulated crests; areas between ridges ornamented with very fine granules. Thoracic sternum wide. Male abdomen triangular. Right cheliped massive.

Etymology. The species name honors Richard L. Squires, prominent paleontologist and prolific publisher on the stratigraphy and paleontology of the Pacific slope of North America.

Remarks. A full description and figures of Costacopluma squiresi and stratigraphic account are given by Nyborg et al. (2009).