70 STALK-EYED CRUSTACEA. 



"■itiulinal depressions running the length of the segment; propodite long, 

 closely set with piliferous squanies on both surfaces ; a longitudinal depres- 

 sion runs from the articulation of the dactjlus back to the carpus ; both 

 finders densely pubescent within at base. Ambulatory appendages : meri 

 ruffose, with spinnles on anterior margin, and a spine at the posterior angle 

 of the distal end of the first and second pairs. The surface of the abdomen, 

 sternum, and outer maxillipeds is thrown into setiferous folds or ridges. 



Color (in alcohol) : reddish, lighter below, the pigment assuming the 

 form of spots on the basal parts of the abdomen ; a large blood-red spot 

 on the propodite of the outer maxillipeds. 



Carapace, 5X5 mm. ; cheliped, 34 mm. ; carpus, 10.5 mm. ; chela, 20 mm. 



One male, taken with the preceding species on the reef at Panama at low 

 tide, March 12. 



In the shape of the carapace and the front this species bears a close 

 resemblance to Peirolisthes sexspiiioms (Gibbes) and P. occideniaUs Stimps., but 

 the transverse ridges are more broken anteriorly, while posteriorly they 

 extend uninterruptedly across the whole width of the cai-apace, being here 

 more perfectly developed and less broken than in the two species named 

 above. The carpus and claw, moreover, are longer and narrower, the ante- 

 rior margin of the carpus is three-toothed instead of five-toothed. The 

 squames of the carpus and claw do not tend to widen out into ridges or folds 

 on either the upper or lower surfaces, but preserve the form of close set 

 imbricated scales over the whole surface, including the space between the 

 longitudinal depressions of the carpus and along the depressed line of the 

 propodite. The form of the carpus approaches nearer to that of Pctrolixthcs 

 armahis (Gibbes),* but the present species may be readily distinguished from 

 P. armahis by the prominent rugce of the carapace, and squames of the che- 

 lipeds. From P. edwardm (Sauss.) the present species is distinguished 

 by its longer chelipeds, by the ridges of the hinder part of the carapace 

 extending clear across the carapace without interruption, etc. The ridges 

 of the frontal lobes are much more strongly developed in P. agussizii than in 

 any of the allied species mentioned above. 



• Porcellana armata Gibbes, Proc. Amer. Assoc. Adv. Sci., 3d Meeting, p. 190, 1S50. Dr. Stimpsoii, 

 ■when labelling the Crustacea in the Smithsonian Institution and Museum of Comparative Zoology, separated 

 the Panama specimens of PetroUxlhcs armatus under the name of Peirolisthes similis, sp. nov., and specimens 

 so labelled were afterward sent to the Jardin des Plantes, Paris. These were seen by Professor Henderson, 

 and are referred to in Ids report on the "Challenger" Anomura, p. 109, as P. similis Stimps. But Slimpson, 

 in publication, referred these specimens to P. armatus (Ann. Lye. Nat. Hist. N. Y., VII. 74, 1859), and 

 never, so far as I can learn, published his P. similis. 



