Periproctia hexachaetata sp. nov.

(Figs. 151, 152)

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21274) anddissectedparatype (♀, figured) from Lissoclinumpatella (Gottschaldt, 1898) (MNHN-IT-2008- 5014 = MNHNA2/LIS/157), CRRFOCDN 5762-W, Boia Boia Waga Island, Papua New Guinea (10°12.26’S, 150°44.75’E), depth 10 m, 27 May 1998.

Etymology. The specific name is from the Greek hexa (=six) and chaet (=a bristle), alluding to the presence of 6 setae on the maxilliped.

Descriptionoffemale. Body (Fig. 151A) slender, cylindrical, 925 μm long; prosome 727 μmlong and 200 μm in dorsoventral depth. Four pedigerous somites fused butdiscernibleby retaineddorsal tergitesand constrictions between them: fifth pedigerous somite completely fused with fourth. Freeurosome (Fig. 151B) 5-segmented, with nearly parallel lateral margins; genital somite 108 μm wide, onlyslightly widerthan first abdominal somite. Four abdominalsomites 59×88, 53×82, 64×77, and 30×62 μm, respectively; first to third abdominal somites ornamented with 2 rows of minute spinules ventrally. Anal somite with pair of smooth ventral protuberances. Caudal rami widely separated from each other at base and directed posterolaterally; each ramus (Fig. 151C) subrectangular, about 1.3 times longer than wide (24×19 μm); armed with 3 claws and 3 naked setae; lengths of claws 24, 17, and 12 μm; smallest dorsal claw thin.

Rostrum similar to that of P. obtusa sp. nov., as long as wide (54×54 μm), with small beak-like process at apex. Antennule (Fig. 151D) 94 μm long and 7-segmented; armatureformula 5, 13+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; 4 setae on each of first and second segments pinnate. Antenna (Fig. 151E) 4- segmented; coxashortand unarmed; basis short, wider than long, with large outer distal seta representing exopod; first endopodal segment with 1 seta on inner margin; compound distal endopodal segment about 2.9 times longer than wide (47×16 μm), ornamented with spinules on outer margin; armed with 6 setae (grouped as 1, 2, and 3) plus slender terminal claw, about half as long as segment,

Labrum missing. Mandible (Fig. 151F) with 5 teeth, 2 needle-like spinules between second and third teeth, and 1 smallsetaoncoxalgnathobase; basiswith 1 medial seta; exopod with 5 setae, distal outer seta shorter than other 4; endopod with 2 and 5 setae on first and second segments, respectively. Maxillule (Fig. 151G) with 7 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on each basis and exopod, and 4 on endopod. Maxilla (Fig. 151H) with 9 setaeonsyncoxa (grouped as 3, 1, 2, and 3), 2 on basis, and 1, 1, and 2 setae on first to third endopodal segments, respectively. Maxilliped (Fig. 151I) armedwith 5 (2+3) medial setae and 1 apical seta.

Legs 1–4 each with 3-segmented exopod and 2- segmented endopod (Fig. 152 A-C). Outer seta on basis of leg 1 large, as typical for genus. Inner setae on exopod and second endopodal segment of leg 1 small. Inner seta absent on second exopodal segment of legs 3 and 4. First and second exopodal segments of legs 2–4 with strong dentiform outer distal process. Inner seta on first exopodal segment of legs 2 and 3 very large, more than twice as long as exopod. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 151B) small, consisting of small outer distal extension on posteroventral margin of somite, tipped with naked seta, and tiny free exopod with naked apical seta.

Male. Unknown.

Remarks. The most characteristic feature of P. hexachaetata sp. nov. is the possession of only 6 setae (5 medial and 1 apical) on the maxilliped. This armature pattern of the maxilliped has not previously been recorded in any species of Periproctia . The armatureof the endopod of leg 4 is also characteristic because the endopod has an unarmed first segment and carries 7 setae on the second segment: this combination has not been found in any congeners (Table 3).