96 NEOTROPICAL PSELAPHIDAE 



form, as long as second, slightly impressed medianly and the posterior margin 

 nearly straight; all sternites little modified. Abdomen from a lateral view 

 ventrally concave in the antero-posterior axis. 



Prosternum simple, with no longitudinal median carina. Metasternura long, 

 longer than second and third sternites united, with the basal half medianly 

 slightly sulcate. Middle coxae contiguous. Posterior coxae obliquely conical, 

 very short, and just perceptibly separated by the metasternum. 



Femora slightly, equally inflated. Middle trochanters with the ventral face 

 shortly produced into a thin subcarinated crest. Middle tibiae with a prominent 

 rounded tubercle or uncus on the internal face at apical three- fourths. Tarsi 

 with two unequal claws, the first claw large and prominent, the second claw 

 half as long as first but very much thinner and not discernible at low magnifi- 

 cations since it is closely appressed to the first, the tarsi appearing to be single- 

 clawed. 



Female Allotype. As in the male holotype, save that (a) the abdomen when 

 seen from a lateral view is not ventrally concave, but straight in the antero- 

 posterior axis, (b) sixth sternite strongly bisinuate at the posterior margin, the 

 median third extending as a short rounded lobe, (c) middle trochanters normally 

 rounded on ventral face, (d) middle tibiae normal, without prominent uncus 

 of male. 



Described on six specimens all collected by Dr. E. C. Williams, Jr., on 

 Barro Colorado Island, Gatun Lake, Panama Canal Zone, as follows: Holotype 

 male, Paratype male and two Paratype females on July 25, 1938, from floor- 

 mold sample No. 164; Allotype female and Paratype male on July 25, 1938, 

 from floor-mold sample No. 134. 



I am pleased to name this isolated species for my friend, Dr. Williams, 

 who spent a summer with me at the Institute for Research in Tropical America 

 at Barro Colorado Island. The series of specimens shows some variation in sev- 

 eral structural features: the median vertexal fovea varies in the paratypes 

 from a deep to a shallow fovea; the transverse carina at elytral base varies 

 from a triarcuate carina with three small foveal pits, to quadriarcuate with 

 four small foveal pits; the pronotal disc is perfectly simple, evenly convex in 

 five of the specimens, but in one male paratype the disc has a faint, vestigial, 

 median, longitudinal, depression rather like a stria. With more material, this 

 variant may prove to be a distinct variety. Otherwise the series is perfectly 

 homogeneous. The secondary sexual characters of the males are few but dis- 

 tinctive, the short laminoid tubercle of the middle tibiae being obvious and 

 constant. 



In a slide mount of a paratype female certain additional features may be 

 noted: (a) the gular fovea resolves into two minute foveae, each with its floor 

 attached to the supratentorium, (b) the apical prosternal margin is dentate, 

 (c) the lateral prosternal foveae are present, and close to each other, and be- 

 tween them there is a very short, median, longitudinal carina for the basal fifth 

 of the prosternum, (d) the foveae of the meso- and metasternum are well 

 formed; II present on each side at union of prepectoid, mesoepistemum and 



