344 COSTA RICAN EPIGOMPHUS (oDONATa) 



about eleven impressed lines (11), some of them subparallel to 

 their next neighbors, others diverging; the more dorsal of these 

 are nearer together. 



No post genal cicatrices are visible on this female. That of June 6 shows 

 what may be faint scars but these are asymmetrically placed. The female 

 taken by Biolley presents two pairs of approximately bilaterally symmetrical 

 scars, and these have been added to figure 22, pgc. The female from Estrella 

 shows no cicatrices, the pit, ridge and groove on each side of the rear of the 

 head are much less pronounced than in the other three females. 



The following suggestions as to the relations of the male ap- 

 pendages to the female head, when pairing, seem plausible: 

 That the lateral apical angles (PL XIV, fig. 20, p') of his superior 

 appendages are received by the pits p (fig. 22), the mesal apical 

 angle and the denticles of the inferior apical margin (W) fit into 

 some of the impressed lines II; distended still more widely the 

 mesal apical angles may produce the postgenal scars (pgc) ; each 

 strong posterior tubercle, pot, of her occiput is received within 

 the concave mesal surface (pot') near the base of his superior 

 appendage of the sam.e side of his body; the apices {prs') of his 

 inferior appendage are placed in her parocular grooves (prs), 

 while the transverse dorsal ridges {dor) of her occiput are lodged 

 in the concavity {dor') of the dorsal surface of the undivided basal 

 portion of his same appendages; perhaps the dorsal denticles 

 near the apical margin of this latter (PI. XIV, fig. 20, d) may secure 

 some hold on the longitudinal ridges which separate the five 

 vertex grooves of her head. 



In the vertex of the male the parocular sulci are present but narrower, 

 the median sulcus is shallower and less sharply defined, the lateral ocellar 

 sulci are much shorter antero-posteriorly as the vertex rises cephalad from its 

 hind margin to an elevation immediately caudad to, and of about the height 

 of, each ocellus, the two elevations thus formed being separated from each 

 other by the median sulcus; the lateral ocellar sulci likewise are much less 

 sharply defined from adjoining sulci than in the female. 



The occiput of the male lacks the pair of low transverse dorsal ridges, its 

 hind margin is less emarginated in the middle and the lateral posterior tub- 

 ercles are much shorter and less pronounced. 



On the rear of the male's head, the homologuc of the subvertical ridge of 

 the female can be recognized in a similar but more rounded swelling, but 

 ■pit, groove and impressed fines, as described for her, are absent. 



