190 PROCEEDINGS OF THE NATIONAL MUSEUM vol. io8 



genera, although manifesting distinct specific and subspecific char- 

 acters in the shape of the receptacle and valves. 



Range: Southeastern United States, from extreme western South 

 Carolina and eastern Tennessee south and west through Georgia and 

 Alabama to Mobile Bay, the Mississippi Delta, and the upland parishes 

 of northwestern Louisiana, north through Mississippi into extreme 

 southwestern Tennessee. 



Species: Two, separable by the characters stipulated in the fol- 

 lowing key. 



Key to the species of Pachydesmus 



1. Small species, less than 50 mm. in length; collum not wider than the following 

 tergite; interzonal furrow open and distinct across sternites; femora of legs 

 longer than coxae and prefemora combined; podosterna of males without 

 transverse ridge between the second legpair . . . clarus Chamberlin (p. 190) 

 Larger species, from 50 to 80 mm. in length; collum considerably wider than the 

 following tergite; interzonal furrow reduced to a mere suture across sternites; 

 femora of legs about equal in length to the prefemora; podosterna of seg- 

 ments 10-17 of males with distinct transverse ridge between the caudad 

 legpair crassicutis Wood (p. 195) 



Pachydesmus clarus (Chamberlin) 



Figures 1,6, 6 



Fontaria clara Chamberlin, 1918b, p. 372. — Attems, 1938, p. 167. 



Pachydesmus kisaichinsis Chamberlin, 1942, p. 4, fig. 8 (Kisatchi, Natchitoches 



Parish, La., type in Chamberlin collection). 

 Pachydesmus clarus Loomis and Hoffman, 1948, p. 53. — Causey, 1955, p. 25. — 



Chamberlin and Hoffman, 1958, p. 43. 



Type specimens: Male holotype and paratypes of both sexes 

 (MCZ), male paratype (USNM 2323), collected at Creston, Natchi- 

 toches Parish, La., by Karl P. Schmidt in February and March 1915. 



Diagnosis: A small species of Pachydesmus separable from crassi- 

 cutis by the characters stipulated in the foregoing key to species. 

 The reduction of the secondary tibiotarsus to a shortened acicular 

 spine and the corresponding diminuation of the coxal apophysis are 

 additional specific characters peculiar to the male sex. 



Description: Of male paratype: Length, 48 mm., width of 10th 

 segment, 9.0 mm. Segments 5-15 of approximately same width. 



Front of head smooth and polished, vertigial groove rather deep 

 just above level of antennae; genae inflated and with distinct median 

 impressions. Two frontal, two subantennal, and four supra-antennal 

 setae present. Antennae set rather close at base, separated by a dis- 

 tance considerably less than length of 2d article. Articles 2-4 similar 

 in size and shape, 6th about same length but less clavate, 7th semi- 

 globose with four well-separated bacilliform sensory cones. Articles 

 1-3 almost glabrous, 1-5 with five or six macrosetae at their distal 



