536 bulletin: museum of comparative zoology. 



fourth to seventh, o^jfyV^J of the eighth and ninth, ^ ' ,' 7 o i of the 

 tenth, q'q' g'g' 2 ', of the eleventh, ^ ^' .-,' J 9 ! of the twelfth, q' q' 2' 2' 2 ' ^^^ 

 dorsal tibial spines equal; of the thirteenth, p' °' '^' ^' ^ , the caudal dorsal 

 tibial spine small; of the penult, q'"'^'^'° , claws 3; (anal legs missing 

 in type) none of the coxae at all armed. 



Tibial process of penult legs of male dorsal in position; shorter and 

 lower than in simplex, more crest like; not very conspicuous. 



Length near 20 mm. 



Locality. — Mexico: Distrito Federal; Esclava (O. W. Barrett). 

 Type, M. C. Z. 1742; one male. 



Closely allied with the preceding species but readily separated by 

 differences in spining of legs (e. g. in total lack of coxal spines) ; clearly 

 by differences in the position and form of the tibial lobe on penult 

 legs of the male; and by differences in proportions, etc. 



Labrobius, gen. nov. 



Lateral marginal breaks of head very weak or obsolete. 



Antennae short or intermediate; articles from 29 to 57. 



Eyes composed of seriate ocelli. Single ocellus clearly differenti- 

 ated. 



Prosternal teeth 2 + 2; line of apices from straight to a little re- 

 curved. Spines slender, bristle like. Sinus distinct, more or less 

 u-shaped. 



Posterior angles of ninth, eleventh, and thirteenth or of seventh, 

 ninth, eleventh, and thirteenth dorsal plates produced. 



Coxal pores circular; uniseriate. 



Claw of female gonopods strictly entire as usual, spines stout, 

 subconical, 2 + 2. 



Anal legs in male with fifth joint bearing at distal end on dorsal 

 or dorsomesal surface a conspicuous, laterally compressed crest. 



Posterior coxae dorsally armed or else wholly unarmed dorsally 

 but armed laterally instead. Dorsal spines of anal legs 1, 0, 3, 1, to 

 0, 0, 3, 2, 1; ventral 0, 1, 3, 2, 1; claws 2. Dorsal spines of penult 

 legs 1, 0, 3, 2, 2 or 0, 0, 3, 2, 2; ventral 0, 1, 3, 3, L Dorsal spines of 

 first legs 0, 0, 1, 1, 1 or 0, 0, 2, 1, 1; ventral, 0, 0, 0, 0, to 0, 0, 1, 1, 1. 



Length 10-13 mm. 



Genotype. — Labrobiiis minor, sp. nov. 



In addition to the genotype and L. delus, sp. nov., L. sontus (Cham- 

 berlin) and L. vulcani (Pocock) also belong in this genus. 



