NATURAL SCIENCES OF PHILADELPHIA. Ill 



CENTRURUS PnAIODACTYLUS. 



C. brunneo-fulvus; cephalothorace sparse puactato, medio leviter canaliculato, 

 antico et abbreviate et rotundato et nonnihil emarginato, postico transversa 

 sulcato ; manibus caudaque venuste politis et pedibus nonnihil pilosis; 

 palpi robustis, angulis vel valde crenulatis vel denticulatis, articuli tertii 

 superficie antica spinulo unico (interdum duobus) ; manibus valdissime 

 tumidis, longis, indistincte octoplicatis ; digitis latis, robustissimis, modice 

 brevibus, curvatis, marginibus opponentibm acute denticulatis ; pedibus flavis ; 

 abdomine laeve ; cauda breve, cristis superioribus obsoletis, superficie superi- 

 ore nonnihil minute granulata ; articulo quarto baud carinato ; articulo 

 ultimo maxinio, spiculo parvo sine spinulo basali ; pectinis dentibus 7-9. 



The cephalothorax is not produced as far anteriorly as is commonly the 

 case. It is impressed with a faint transverse groove at the position of the 

 median ocelli, and with another, more distinctly defined, on its posterior 

 third. These channels separate three pairs of slightly pronounced elevations, 

 which successively decrease in size from the first. The first joint of the palpi 

 has all of its margins armed with distinct obtuse denticules, excepting only 

 the postero-inferior, which is rounded and concave, and crenate only on its 

 proximal third. The third article is much larger than the second, and has 

 only its anterior margins crenate. Its posterior surface, as well as that of the 

 hand, is sparsely and irregularly punctate. The anterior aspect of the hand 

 is minutely tuberculate. The first joint of the mandibles is very long, almost 

 always extending as far forward as the cephalothorax, and often much beyond 

 it. The distal portion of these organs, with the "pincers," is black. The 

 median eyes are placed upon a single black elevation in the middle third of 

 the cephalothorax. The first two lateral ocelli are somewhat smaller 

 than the median ; the third is much smaller ; the fourth is at right angles to 

 the third, and is still less. The three anterior joints of the tail are short and 

 rather broad. Their superior crests are entirely, and their supero-lateral al- 

 most, obsolete ; their inferior and infero-lateral are well-marked and broadly 

 crenate. All of the ridges of the fourth segment are obsolete. The penulti- 

 mate joint is elongate and slender. Its lower surface is rough, and has two 

 strongly, but obtusely denticulate infero-lateral, and a single, median-inferior 

 crest. The last segment is immensely swollen. Its distal portion is sud- 

 denly and very strongly contracted, and then inflated slightly again, so as 

 to form a knob, as it were, on the base of the sting. 



Length of body, 1 inches ; of tail, 1 inches. 



Hub. Utah Territory. Smithsonian Museum. M. McCarthy, Esq. 



Phrtnps asperatipes. 



P. dilute aurantiacus saturate rubido-brunneo maculatus ; cephalothorace 

 lato, reniforme, abdomineque tuberculis parvis sparsis et granulatis minutis 

 numerosis asperatis ; palpi magnis latis, nonnihil semi-cylindriaceis ; arti- 

 culi secundi superficie antica et spinulis parvis numerosis et uno vel duobus 

 majoribus armata ; articuli tertii margine superiore spinis 4, inferiore spinia 

 5 ; articuli tertio quartique superficiebus posticis tuberculis parvis spinosis in 

 seriebus rectis dispositis armatis ; illius margine superiore ulterius spinis 

 maximis 3 et 2-3 modicis instructo ; margine inferiore spinis magnis 2 et 

 2-3 parvis armato ; articulo quinto spina maxima unica et spinulis modicia 

 duobus instructo ; femoribus tuberculis spinosis numerosis asperatis. 



The color of our single specimen is a very light orange. The cephalothorax 

 has a median longitudinal sulcus distinct anteriorly, but evanescent posteri- 

 orly. A short distance behind the centre of the cephalothorax is a well-defined 

 transverse groove, extending nearly across one-third of its breadth. Posterior 

 to this, and connected with it by the median sulcus (here very well marked), 

 is a transverse furrow similar to the other, but only about one-third its length. 



1863.] 



