16 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 125 
Family DissonrpAE 
Dissonus heronensis Kabata 
FIGuRES 7-9 
Dissonus heronensis Kabata, 1966a, p. 221, fig. 5. 
Host AND DISTRIBUTION.—‘‘Unspecified fish of the family Balisti- 
dae” (Kabata, 1966a, p. 221), Heron Island, Queensland, Australia. 
MareriAL.—7 females and 1 male (USNM 120741) from the gill 
cavity of Balistoides viridescens (Bloch and Schneider). 
MEASUREMENTS (in mm).—5 females and 1 male: 
emale 
mean range male 
Total length, excluding caudal setae 1. 96 1. 82-2. 03 1. 51 
Length of prosome Teas 1. 12-1. 19 0. 88 
Width of prosome 0. 85 0. 79-0. 88 0. 67 
Length of cephalothorax 0. 87 0. 83-0. 94 0. 61 
Length of genital segment 0. 56 0. 49-0. 63 0. 52 
Width of genital segment 0. 47 0. 43-0. 50 0. 31 
Length of abdomen 0. 20 0. 11-0. 25 0.11 
Length of egg strings (8 strings) 1. 43 1. 37-1. 48 
Derscription.—Female cephalothorax (fig. 7b) consisting of cepha- 
lon and first 2 thoracic segments, strongly arched in transverse 
section. Frontal region (fig. 7g) membranous, narrow, forming slightly 
less than 10 percent of length of cephalothorax; with small, median 
notch in anterior margin. Lateral margin irregularly convex, with 
fine membrane posteriorly. Posterior lateral cephalothoracic region 
lobate, projecting to posterior half of free second pedigerous segment. 
Major dorsal cephalothoracic grooves consisting of pair of convex 
grooves extending anteriorly from junction of inner margin of pos- 
terior lateral cephalothoracic region and outer margin of free second 
pedigerous segment, terminating lateral and slightly posterior to 
pair of small, slightly projecting heavily sclerotized ridges. Ocular 
region indistinct, situated on median longitudinal axis of body, 
anterior to ridges. 
Female free second pedigerous segment slightly less than twice as 
wide as long, division between segment and cephalothorax distinct; 
lateral regions lobate, extending posteriorly to posterior region of 
third pedigerous segment; lobes with membrane along outer margin. 
Third pedigerous segment distinct from second, width slightly more 
than twice the length, segment without posterior extensions of lateral 
regions. Fourth pedigerous segment distinct from third, width slightly 
more than one and one-half times the length; broadest medially, 
tapered to anterior and posterior ends. 
Female genital segment (fig. 7d) generally ovoid although shape 
variable; indistinctly separable from fourth pedigerous segment. 
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