268 NEOTROPICAL PSELAPHIDAE 



Abdomen with seven sternites with a length ratio of 11/2/1/-33/.33: 

 .2/1.33/1.33. First five simple and convex; sixth with an erect, transversely 

 oblong lamina arising medianly at apical four-fifths. On using high magnifica- 

 tion this peculiar plate is seen to consist of erect, slender, sharp teeth so that 

 the plate in reality, is a comb; seventh as long as sixth, in two parts, a right and 

 a left subtriangular plate. In the holotype and some paratypes, these plates are 

 widely separated and the partially extruded penis protruded between them ; in 

 some paratypes the plates are closed, the line of junction forming a median, 

 longitudinally arcuate carina. 



Intermediate trochanters with a small, blunt tooth near base on ventral 

 face. Femora simply inflated. Tibiae gradually thicker to apex and apically pu- 

 bescent on ventral face; posterior tibiae with a short apical spur. Tarsi relatively 

 short and thick, first segment small, triangular; second and third much longer, 

 second twice as long as third; third with a long, thick primary claw and an 

 accessory bristle. Posterior coxae widely separated, their separation equal to 

 the metasternal length. 



Metasternum medianly, simply and broadly concave. 



Allotype Female. Similar to male save that (1) occiput is not medianly 

 tuberculate, (2) six sternites only, all unmodified, (3) femora not inflated, 

 (4) intermediate trochanters unarmed. 



Described on nineteen specimens, all collected from soft, moist, decayed 

 log mold or sifted from leaf mold of the rain forest floor at Barro Colorado 

 Island, Gatun Lake, Panama Canal Zone, during the day. One female paratype 

 and two males paratypes collected July 20, 1935, by Alfred Emerson. The rest 

 collected by the author during the summer of 1936 by the author as follows: 

 female paratype at Drayton 16 (July 25) ; holotype at Zetek 23 and allotype 

 at Zetek 23 (July 27) ; two male paratypes at Zetek 3 (July 28) ; one male and 

 two female paratypes at Zetek 17 (July 28) ; two female and two male para- 

 types at Pearson 2 (July 29) ; one male and three female paratypes at Armour 

 10 (July 30). 



Because of its relatively wide insular distribution and abundance, I am 

 inclined to consider this species as a characteristic constitutent of the rain forest 

 log mold. It is strange that none were taken at night at lights. It is of interest 

 also that of nineteen specimens, nine were males and ten females, attesting a 

 normal sex ratio. 



One male collected July 20, 1935, had just pupated. 



I take pleasure in naming this distinctive species for my friend, Professor 

 Alexander Petrunkevitch, with whom I spent many a happy hour collecting 

 in the rain forest. 



At first glance Dalmoburis petrunkevitchii and Buris brunneus appear very 

 similar. Both have the same indefinable habitus of close taxonomic relationship, 

 and at first I had thought that petrunkevitchii could be placed in Buris. Mature 

 consideration of paratypes of Buris brunneus in the U. S. National Museum and 

 direct comparison of these with the present species, showed such a course to be 

 both impracticable and unjustifiable. Both genera agree in such fundamentals 



