COMPLETE HAIG : EASTERN PACIFIC PORCELLANIDAE 55 



Petrolisthes nobilii, new species 

 Plate 1; plate 18, fig. 3 



} Petrolisthes politus, Nobili, 1897, p. 4. Rathbun, 1910, p. 600. Not 



P. politus (Gray). 

 Petrolisthes armatus, Boone, 1931, p. 151 (part). Not P. armatus 



(Gibbes). 



Previous records: Panama. "Panama" [City?]: E. Festa (Nobili). 

 Isia Taboguilla ; Isla Pacheca and Isla Saboga, Islas de las Perlas : W. 

 G. Van Name (Boone). 



Types: Holotype, male, U. S. National Museum Cat. No. 99654, 

 from Isla Taboguilla, Panama, shore; October 31, 1904; collected by 

 the Albatross. Paratypes: 158 specimens from the same and 15 other 

 stations (see Table 12). Museum of Comparative Zoology specimens 

 from Cabo San Lucas and Islas de las Perlas, and American Museum 

 of Natural History specimens from Isla Taboguilla and Islas de las 

 Perlas, were not critically examined during the drawing up of the 

 description and therefore are not designated paratypes. 



Diagnosis: Carapace granulate and plicate; epibranchial spine ab- 

 sent or vestigial, but its position marked by a distinct notch; front 

 sinuously triangular; carpus about two and a half times as long as 

 wide, anterior margin with three low, wide-set teeth, a fourth rarely 

 present ; manus broad, outer margin curved ; merus of walking legs with 

 a row of spines on anterior margin, that of legs 1 and 2 spined at pos- 

 terodistal angle. 



Description: Carapace about as broad as long, or slightly broader; 

 broadest posteriorly, the lateral margins sharply diverging posterior 

 to the epibranchial angle. Gastric, frontal, and orbital regions covered 

 with small flattened granules; epibranchial regions with rough trans- 

 verse plications or large granules, continuing onto the posterolateral 

 margins; posterior portion of carapace otherwise smooth or punctate. 

 Front strongly produced, sinuously triangular, with a deep median 

 sulcus; no supraocular spine. Orbits strongly oblique; outer orbital 

 angle not produced. Epibranchial angle with a distinct notch, but spine 

 absent or vestigial; rarely present. Carapace naked or lightly pub- 

 escent. 



First movable segment of antenna with a strongly projecting, 

 rounded, spine-tipped lamellar lobe; second granular, with a conical 

 projection at the proximal end of the anterior margin; third nearly 



