30 PROCEEDINGS OF THE NATIONAL MUSEUM vol. in 



P. moyohamhus (Chamberlin). To be particularly noticed in the 

 figure is the pronounced indentation of the inner margin of the telo- 

 podite, just above the coxal articulation, A similar peculiarity is 

 likewise to be seen in P. schmitti and P. moyohamhus, and may prove 

 to be a constant generic character. 



Although Chamberlin described the type as being uniformly 

 brown dorsally, I was able to discern traces of two light paramedian 

 dorsal stripes. In my key to species (1953a, p. 304j, P. atratus runs 

 out readily to P.fasciolatus (Silvestri), which, as implied by its name, 

 has a similar color pattern. P. atratus differs from its congener chiefly 

 in the shape of the tibiotarsus of the gonopod and its somewhat 

 larger size. Judged from the similarities of the two, and from the 

 geographic proximity of their type localities, the relationship will 

 probably be found to be a subspecific one. 



It should be noted in passing that the original binomial combina- 

 tion Platyrrhacus atratus as used by Chamberlin is preoccupied in 

 the Diplopoda. Attems (1900) transferred the species named by 

 Pocock (1897) as Polydesmorhachis atratus into the genus Platyrrhacus, 

 the resulting combination existing in the literature for more than 

 a decade. Those who suppress junior secondary homonyms may wish 

 to rename Chamberlin's Colombian species, but my personal pref- 

 erence is to disregard instances of transient combinations resulting 

 from the arbitrary and often ill-advised shifting of names from one 

 genus to another. 



PsammodesTnus schmitti Loomis and Hoffman 



Psammodesmus schmitti Loomis and Hoffman, in Hoffman, 1953a, p. 301, figs. 

 1-4 (type data given as holotype male, USNM 2016, Port Obaldia, Panama). 



This species was described from specimens taken at Port Obaldia 

 on the Atlantic Coast, and Cana in the interior of Darien, both 

 localities being very close to the Panama-Colombia boundary. An 

 additional specimen is at hand from a third locality, the upper Pe- 

 quene River just east of the Canal Zone, collected on March 25, 

 1907, by A. H. Jennings (USNM). This specimen extends the 

 range of the species over 100 miles westward along the Isthmus. 



The gonopods of the specimen match those of the types very closely. 

 Although considerably bleached by the alcohol, the specimen retains 

 enough pigmentation to indicate that the color pattern consisted of 

 a pair of oblique light paramedian stripes on each tergite, each 

 stripe being directed caudolaterad and probably creating the impres- 

 sion in life of a strongly serrated longitudinal light stripe down each 

 side of the dorsum, on the base of the paranota. 



