170 U.S. NATIONAL MUSEUM BULLETIN 2>58 



has a uniarticulate and that of Stomacontion a biarticulate palp. 

 Stomacontion insigne K. H. Barnard (1932) has a uniarticulate first 

 maxillary palp combined with a vestigial fourth maxillipedal palp 

 article, so obfuscating the generic definitions. Both of these species, 

 in addition, have the first coxa subconically narrowed below, indi- 

 cating that they represent a pair of interrelated species grossly 

 divergent from Acontiostoma and Stomacontion. Indeed, one could 

 establish new genera for both of them or provide four subgeneric 

 names under Acontiostoma to denote the four kinds of taxa mixed 

 in this complex. 



Fresnillo fimbriatus, new species 



Figures 43, 44 



Diagnosis^ — -With the characters of the genus. 



Description. — Article 1 of antenna 1 crested, article 3 triangular, 

 article 2 of peduncle and article 1 of flagellum touching, accessory 

 flagellum forming a small scale armed with 2 setae; eye formed of 

 few large, subquadrate ommatidia surrounding a dense, dark mass 

 of pigment; maxillae not clearly analyzed, these appendages or 

 their presumed figments badly shriveled, poorly chitinized (dissected 

 in 5 specimens), the presumed first maxillae by merit of their orien- 

 tation appearing to have lateral lobes representing uniarticulate 

 palps, outer plates medial to palps bearing in some aspects a minute 

 appendage; by assuming a reversal in the direction of pointing one 

 might assume the palp to be the inner plate and the small appendage 

 on the outer plate to be a palp but this is contrary to the expected 

 orientation; maxilla 2 possibly formed of two tiny appendages 

 (plates) attached to a broad basal piece (see figures) ; gnathopod 1 

 simple, article 6 much longer than 5; gnathopod 2 similar to that 

 of Ocosingo, article 6 bearing tasselled setae, apex of article 6 exca- 

 vated and lacking article 7, appearing to have duct leading from 

 basal glandular area (possibly used as poison gland or having a 

 commensal property); body and coxae covered with minute setules, 

 pleonites 3-4 elevated acutely above, pleonites 5-6 very small but 

 distinct; uropod 3 claviform, bearing papulations and lacking any 



Figure 43. — Fresnillo fimbriatus, new genus, new species, holotype, ?sex, 1.2 mm., station 

 38-F-l: a, lateral view; b, antenna 1; c, antenna 2; d, enlargement of article 3 of antenna 

 1 peduncle showing triangular shape and one view of attached accessory flagellum; e, 

 accessory flagellum of antenna 1 after being turned from its position in figure d; f, side 

 of head and mouthpart bundle below, the setose piece representing a lateral view of 

 epiftome-upper lip complex, stippled piece representing mandibular palp; £, mandible; 

 h, an unidentified mouthpart; i, j, two mouthparts believed to be second maxillae, the 

 definitive pieces represented as tiny apical lobules, each pair _of lobules as inner and 

 outer lobes; k, I, m, various mouthparts identified as first maxillae from several individ- 

 uals; n, o, views of maxilliped; IP = inner plate; OP = outer plate; P=base of palp; 

 p, q, gnathopod 1. 



