302 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



Herbstia (Herbstiella) camptacantha, Miers, 1886, p. 49. Holmes, 1900, 



p. 37 (part: not the California or Magdalena Bay specimens). 

 Microphrys depressa, Miers, 1886, p. 83. 



Mithrax (Mithrax) sonorensis Rathbun, 1933, p. 338, pi. 24; type 

 locality, San Pedro Bay, Sonora, Mexico; female holotype, 

 U.S.N.M. No. 67865. 

 Alithrax sonorensis, Steinbeck and Ricketts, 1941, p. 467. 



Type: Male cotype from Acapulco, M.C.Z. No. 991, length 17.1 

 mm, width 14.5 mm. The male cotype from Cape San Lucas, originally 

 in the collections of the Smithsonian Institution, is no longer extant. 



Type localities: Cape St. [San] Lucas, Lower California, John 

 Xantus, collector, and Acapulco, Mexico, Alexander Agassiz, collector. 



Localities subsequently reported, with collectors: Gulf of California: 

 San Pedro Bay, Sonora, and Concepcion Bay, Lower California, S. A. 

 Glassell (Rathbun, 1933, as Mithrax sonorensis) ; Patos Anchorage, 4.5 

 fathoms, Fred Baker, California Academy of Sciences (Rathbun, 

 1924c) ; Port [Puerto] Escondido and San Jose Island, W. J. Fisher 

 (Lockington, as Fisheria depressa) ; Coronado[s] Island, J. Steinbeck 

 and E. F. Ricketts (Steinbeck and Ricketts, as Mithrax sonorensis). 

 Central Mexico: Mazatlan, Hy. Edwards (Lockington, as Mithrax 

 armatusf). Note: All California and west coast of Lower California 

 specimens are treated under Herbstia parvifrons Randall. 



Atlantic analogue: None. A Gulf of California-west coast of Mexico 

 endemic species. 



Diagnosis: Basal antennal article narrow; three outer marginal spines 

 including anteroexternal spine. First movable article of antenna falling 

 short of tip of rostrum ; anteroexternal antennal spine directed forward 

 rather than outward. Male first pleopod tapering, tip acute, slightly 

 recurving, a setiferous fold on concave margin. 



Description: Carapace slightly convex, and the surface very reg- 

 ularly and conspicuously punctate. The cervical suture deep and well 

 marked, the sulci separating the branchial from the cardiac regions very 

 shallow, and no sulcus whatever between the branchial and the rather 

 flattened intestinal region. Twenty small tubercles on the carapace, not 

 including the marginal spines; there are of these tubercles five on the 

 gastric region, four arranged in a transverse line across the middle, the 

 two on either side being approximated ; three on the cardiac region, two 

 on the intestinal, and five on each branchial region. Margin of the cara- 

 pace on each side behind the orbit with fourteen spines; five on the 

 anterolateral and nine on the posterolateral margin. Posterior spines very 



