70 



STALK-EYED CRUSTACEA 



, * 



gitudinal depressions running the length of the segment; propodite long, 

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

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

 fingers densely pubescent within at base. Ambulatory appendages : meri 

 rugose, with spinulcs 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 i^pot 

 on the propodite of the outer maxillipeds. 



Carapace^ 5 X 5 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 PetroUsfMs sexspinosiis (GIbbes) and P. occidenlalis Stimps., but 

 the transverse ridges are more broken anteriorly, while posteriorly they 

 extend uninterruptedly across the whole width of the carapace, 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 fine of the 

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

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

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



lipeds. 



From P. edwardsii (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, agassizii than in 

 any of the allied species mentioned above. 



* Porcellana armaia Gibbes, Proc. Amcr. Assoc. Adv. Sci,, 3d Meeting, p. 190, 1850. Dr. Stimpson, 

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

 the Panama specimens of PeiroUsikes armatus under the name of Peirolislhes similis^ sp. nov., and spcelinens 

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

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

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

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



