1918] Myriopods from Georgia and Louisiana 377 



Basal plate trapcziform, the anterior margin widely evenly concave. 

 About one-third as long on median line as the cephalic plate; three and 

 a half times as wide as length at middle. 



Antennae moderately short, three times as long as the cephalic- 

 plate. Attenuated distad. The ultimate article equal in length to 

 the two preceding taken together. Proximally sparsely hirsute, becom- 

 ing densely so distad with the hairs shorter. 



Prosternum much wider than long (21:13). Anterior margin 

 forming a very obtuse re-entrant angle with the edge smooth and 

 strongly chitinized except at middle. Joints of prehensors very short, 

 the distal end of the first one on the mesal side scarcely cephalad of the 

 anterior edge of the prosternum. Claws when closed, falling much 

 short of attaining the front margin of head. All joints wholly unarmed. 



Prescuta in middle region a half or a little more as long as scuta, 

 becoming very short cephalad and in the extreme posterior region. 



.First four spiracles broadly vertically elliptic, the others circular: 

 decreasing in size gradually from the first, which is large, caudaci. 



First legs much reduced in size, the second ones being abruptly 

 longer and stouter. Posterior pairs proportionately more slender than 

 the anterior and much longer. 



None of the ventral plates at all suleate. Ventral pores in anterior 

 region distinct and numerous, forming a continuous transverse band 

 posteriorly, which may extend slightly forward at the middle andja 

 small subcircular area in each anterior corner. Posteriorly the anterior 

 areas disappear and the pores of the posterior band become few and less 

 distinct. 



Last ventral plate very wide, wider than the preceding stemitc. 

 Sides strongly convex, converging caudad. Caudal margin straight. 

 Coxopleural pores obscure, covered by the ventral plate. 



Anal legs much longer and stouter than the penult in both sexes. 

 The sixth article abruptly much more slender than the fifth, the append- 

 age replacing the claw minute. 



Pairs of legs, 61-63. 



Length up to 45 mm. 



Locality. — La. : Creston, March 5, March 9, and March 20. 

 one specimen being secured on each of these dates. 



Helembius gen. nov. 



Of the genera of smaller lithobiids previously known to occur in 

 the southeastern United States this genus is like Nampabius and Garibius 

 in having the number of articles in the antennae definitely fixed at 

 twenty. It differs from those genera in having the anal and penult 

 legs of the male simply inflated and wholly without special lobes on 

 either pair. In the sparse development of spines on the legs and their 

 complete absence from the cox«, the type species suggests Nampabius, 

 which differs, aside from the possession of the highly characteristic lobe on 

 the penult legs of the males, in the characteristic U-form of the median 

 incision of the prosternum and in the small, not enlarged, single ocellus. 



