Material examined: Holotype: Non­ovigerous female, P 61357, body length 3.1 mm, Sta. SO 5­83 ­B2, 19º56,7’S. 117 º53,6’E. Depth 41 m. Paratypes: 2 Non­ovigerous females, P 61358, same locality. Collected by staff on board RV “Soela” CSIRO 1983.

Other material: 24 Non­ovigerous female, P 52206, same locality. 2 females, P 52191, Sta. No. SO 2­83 ­B 12, Lat. 19 º 56.9 'S, Long. 117 º 53.7 ' E. Depth 43 m. 9 females, P 52349, Sta. No. SO 4­83 ­B 1, Lat. 19 º 58.9 'S, Long. 117 º 51.7 'E. Depth 42 m. 1 female, P 52351, Sta. No. SO 4­83 ­B 7, Lat. 19 º 30.8 'S, Long. 118 º 49.4 ' E. Depth 38 m. 3 females, P 52195, Sta. No. SO 3­83 ­B 2, Lat. 19 º 56.4 'S, Long. 117 º 53.9 ' E. Depth 44 m. 1 female, P 52204, Sta. No. SO 4­83 ­B 17, Lat. 20 º00.2'S, Long. 117 º00.5'E. Depth 52 m. 1 female, P 52199, Sta. No. SO 4­83 ­B 2, Lat. 19 º 56.7 'S, Long. 117 º 53.8 ' E. Depth 42 m. 1 female, P 52200, Sta. No. SO 4­83 ­B 10, Lat. 19 º05.0'S, Long. 118 º 57.9 'E. Depth 86 m. 1 female, P04971, Sta. No. SO 2­83 ­B 3, Lat. 19 º 55.9 'S, Long. 117 º 56.8 'E. Depth 42 m. 4 females, P 52191, SO 2­ 83 ­B 12, Lat. 19 º 56.9 ', Long. 117 º 53.7 'E. Depth 43m. 1 juvenile, P 52208, Sta. No. SO 5­ 83 ­B 5, Lat. 19 º04.8'S, Long. 118 º 50.7 'E. Depth 81 m.

Diagnosis: Antennal 2 article 2 as deep as long, with disto­ventral quadrate process extending just past articulation of article 3 and 4; article 3 inserted dorsally into article 2, rounded disto­dorsally and armed with blunt, subapical tooth. Labium without antero­lateral projections. Uropod exopod about half as long as endopod.

Description (adult female).

Body (Fig. 3 A): Slender, sub­cylindrical, approximately 8 times longer than broad.

Cephalothorax (Fig. 3 B): Shorter than length of pereonites 1 and 2 together, width 0.75 length, antero­lateral corners curving anteriorly. Eye lobes smoothly curved.

Pereonites: Pereonite 1 wider than long, extending over cephalothorax at pereopod attachment. Pereonites 2, 3 and 5, longer than wide. Pereonites 4 and 6 length subequal width.

Pleon: Pleonites 1­5 subequal, width approximately 4.0 length. Pleotelson as long as 2 last pleonites together.

Antennule (Fig. 3 C): Shorter than cephalothorax. Article 1 greatly swollen, only marginally longer than wide, longer than combined length of rest of antennule (excluding setae), with several sensory setae on inner margin and 2 short simple distal setae. Article 2 more than half as long as article 1, distal margin with 2 long simple setae and 2 short sensory setae. Article 3 one quarter as long as article 2, with 1 long setulated and 1 simple distal setae. Article 4 half as long as article 2, with 5 distal serrated setae twice as long as antennule.

Antenna (Fig. 3 D): as long as combined length of 3 first articles of antennule. Article 1 smooth, as long as article 3. Article 2 with 1 distal dorsal simple seta, ventral process extending beyond article 3 with on distal simple ventral seta. Article 3 quadrate with short dorsal spiniform seta. Article 4 longer than article 5, armed distally with 1 long serrate seta, 1 short simple seta and 3 sensory setae. Article 5 half as long as article 4, with 2 long setulated distal setae. Article 6 minute, with 2 setulose setae longer than antenna itself, 2 long­ and 1 short simple setae.

Mouthparts: Labrum (Fig. 3 E) setose, with rounded apex. Mandibles (Figs. 3 F & G) molar longer than incisor, left mandible with strongly defined lacina mobilis with several denticulations, incisor unidentate, right mandible with broad and bidentate incisor. Maxillule (Fig. 3 H) with 7 thick terminal setae and row of setae, palp not recovered. Maxilla (Fig. 3 I) triangular. Labium (Fig. 3 J) tapering distal and with numerous distal setulated scales. Maxilliped (Fig. 3 K) endites with 1 simple seta on inner corner and 2 flat distal setae; palp article 1, outer margin longer than inner, smooth; article 2, inner margin longer than outer, with 3 setulated setae on inner margin; article 3, with 4 setulated setae on inner margin; article 4, rectangular, inner margin with 4 setulated distal setae, outer margin with 1 setulated seta. Epignath not recovered.

Cheliped (Fig. 3 L): Basis twice as long as wide with 1 minute simple distal seta,. Merus ovoid, with 1 simple seta medially on ventral margin. Carpus oval, marginally longer than basis, with 2 simple setae on ventral margin, 2 setae on dorsal margin. Propodus slender, with 2 distal dorsal setae at dactylus insertion and 1 simple seta medially at dactylus insertion. Fixed finger with strong bifurcated apex, 2 simple setae on ventral margin, 3 on cutting edge. Dactylus narrow, with 1 seta on its dorsal surface.

Oostegites: originating from pereonites 1­4.

Pereopod 1 (Fig. 4 A): Longer than other pereopods. Coxa with 1 simple seta. Basis as long as 3 succeeding articles combined, with 1 proximal simple setae on ventral margin. Ischium with 2 simple setae on dorsal margin. Merus longer than carpus, with 1 simple distal seta on dorsal margin. Carpus two thirds as long as propodus, with 2 short simple distal setae. Propodus as long as merus, tapering distally, with 2 short and 1 long simple distal setae. Dactyl and terminal seta together longer than propodus.

Pereopod 2 (Fig. 4 B): Similar to pereopod 1, except: Merus smooth and as long as carpus. and propodus as long as dactylus and terminal setae combined.

Pereopod 3 (Fig. 4 C): Similar to pereopod 2, except: Ischium smooth, merus with 1 simple seta, carpus smooth, dactyl and terminal seta together longer than propodus.

Pereopod 4 (Fig. 4 D): Basis stout with 1 simple and 1 sensory distal setae. Ischium with 2 simple ventral setae. Merus ovoid, longer than carpus, with 1 simple, 1 short stout denticulated seta, and denticulated scales. Carpus shorter than propodus, with denticulated scales, 1 simple setae and 4 short stout denticulated distal setae. Propodus with 1 dorsal sensory, 1 long serrated, 1 spiniform, and 1 spiniform setulose distal setae. Dactyl and terminal spine fused into claw with setules.

Pereopod 5 (Fig. 4 E): As pereopod 4, except: Basis with 1 simple dorsal seta. Carpus with 3 spiniform denticulated distal setae.

Pereopod 6 (Fig. 4 F): As pereopod 4 except: Basis smooth, ischium with 1 simple seta, merus with denticulated scales and 1 short denticulated setae, carpus with 4 short denticulated distal setae, propodus without sensory seta but with 2 spiniform subdistal and 3 stout setulated distal setae as long as dactylus.

Pleopods (Fig. 4 G): All 5 pairs similar. Protopod trapezoidal. Exopod armed with 19 plumose setae. Endopod, inner margin finely setose, with 14 plumose setae, 2 distal setae shorter and stouter than rest.

Uropods (Fig. 4 H): Protopod elongated, smooth. Endopod articulation weak, with 1 simple and 2 sensory setae at midlength on second article element and 4 long­ 1 short simple­ and 1 sensory distal setae. Exopod with 3 short­ and 1 long simple setae.

Male: unknown

Etymology: Named after the preferred habitat of most Bathytanais species (Latin: arena­mans = sand­lover).

Habitat: Specimens living in sandy bottom at 41 m depth on the Northwest Australian shelf off Western Australia. Specimens were found in tubes consisting of sand grains and mucus.

Remarks: Bathytanais arenamans is distinguished from the other known members of the genus by the shape of antennal article 1 with is swollen and only marginally longer than wide. B. arenamans superficially resembles B. juergeni. Article 3 of antenna 2 in B. arenamans, however, has a subapical blunt, tooth­like seta instead of the acute disto­dorsal process that characterizes B. juergeni. Also ventral process of antenna article 2 does not extend beyond article 3 in B. juergeni.