40 
SYSTEMATICS 
Family AMEIRIDAE Monard, 1927 
Genus INERMIPES gen. nov. 
DIAGNOSIS. Ameiridae. Body elongate, cylindrical, and vermi- 
form without distinct surface ornamentation except for ventral 
spinule patterns on abdomen. Cephalothorax and other somites with 
smooth posterior margin. Genital and first abdominal somites com- 
pletely fused forming double-somite; original segmentation not 
discernible. Genital field with small copulatory pore located in 
median depression. Anal operculum well developed. 
Sexual dimorphism in antennule, P1 inner basal spine, P5, P6, 
genital segmentation and abdominal spinulation. 
Rostrum fused to cephalothorax, not defined at base. Antennule 
8-segmented in, 10-segmented and subchirocer in d; segment 1 
without seta; aesthetascs on segments 4 and 8() or on 5 and 10 (d); 
apical acrothek consisting of minute aesthetasc and 2 setae. Antenna 
with separate basis and endopod; exopod minute, with | seta. 
Mandible with 2-segmented palp, comprising unarmed basis and 
endopod with 4 setae. Maxillule with strongly developed arthrite, 
with 2 naked seta on anterior surface and 8 spines/setae around distal 
margin; coxa with 2 setae and | spine; palp cylindrical with 5 setae, 
probably representing basis only. Maxilla with trisetose endite on 
syncoxa; allobasis drawn out in remarkably long claw; endopod a 
small bisetose segment. Maxilliped with unarmed syncoxa; basis 
elongate, with very long endopodal pinnate claw. 
P1 with 3-segmented rami; basis without outer seta, inner spine 
sexually dimorphic; exp-1 elongate, exp-2 without inner seta, exp-3 
with 4 elements; endopod with formula [1.0.020]. 
P2—-P4 with 3-segmented exopods and 1-segmented endopods. 
Bases without outer seta. Exp-1 markedly elongate; exp-2 with very 
strong inner seta; apical setae of exp-3 very long. Endopods minute, 
with very long apical seta(e). Armature formula: 

Exopod Endopod 
b2 0.1.022 010 
P3 0.1.022 020 
P4 ORII22. 010 
PS rudimentary with baseoendopod fused to somite and repres- 
ented only by outer basal seta. Exopod a small segment with | seta 
in 2 and | multipinnate fused spine plus | setain d. P6 rudimentary, 
forming unarmed median operculum in 9; asymmetrical in d (with 
dextral or sinistral configuration), represented by opercular un- 
armed plate. 
Caudal ramus short, with 7 setae; seta V longest. 
Spermatophore extraordinarily large, longer than half the body 
length. 
TYPE AND ONLY SPECIES. Jnermipes humphreysi gen. et sp. nov. 
ETYMOLOGY. The generic name alludes to the absence of the outer 
seta on the bases of the swimming legs. Gender: feminine. 
Inermipes humphreysi sp. nov. 
TYPE LOCALITY. Barrow Island, Western Australia (37°50'46"N, 
31°31'35"W), stn BES 792, borehole, 50—55m deep, | December 
1992. 
TYPEMATERIAL. Holotype 2 dissected on 9 slides (WAM C24414). 
Paratypes deposited in NHM are 12 dissected on 8 slides (BMNH 
W. LEE AND R. HUYS 
1999.1106), BES 792, depth 50-55m, 1 December 1992 and 922, 9 
36 in 70% alcohol (BMNH 1999.1107—1124), BES 793, 1 Decem- 
ber 1992. Paratypes deposited in WAM are (a) 1 6 dissected on 7 
slides, and 499, 6 dd in 70% alcohol, BES 792, depth 50—-55m, 1 
December 1992, (b) 1 6d in 70% alcohol, BES 798, depth 45—50m, 
2 December 1992, and (c) 522, 15 36 in 70% alcohol, BES 810, 
depth 50-55m, 2 December 1992 (WAM C24415-24417). All 
specimens are from the type locality and were collected by Dr W.F. 
Humphreys using a plankton net with a 125 m mesh and of a size 
suitable for the borehole (Pesce et al., 1996a). 
DESCRIPTION 
FEMALE. ‘Total body length 540-667um (n=10; mean = 592 um; 
measured from anterior margin of rostrum to posterior margin of 
caudal rami). Largest width measured at posterior margin of genital 
double-somite: 106m. Genital double-somite swollen. No distinct 
demarcation between urosome and prosome (Fig. 1B). 
Cephalothorax with smooth posterior margin; pleural areas small 
and rounded; sensillae and few pores present as illustrated in Fig. 
1A-B. Rostrum not defined at base (Fig. 1B), with pair of tiny 
sensillae near apex. 
Pedigerous somites completely smooth. All prosomites without 
defined hyaline frills; hind margin smooth; separated by large 
membranous areas. Body not markedly constricted between indi- 
vidual somites. P4-bearing somite distinctly narrower than preceding 
ones. 
Urosome (Fig. 1!A—B) 5-segmented, comprising P5-bearing 
somite, genital double-somite and 3 free abdominal somites. P5- 
bearing somite, and genital double-somite without surface 
ornamentation, except for dorsal pairs of sensillae. Free abdominal 
somites with several rows of minute spinules laterally (Fig. 1A) and 
ventrally (Fig. 2C); hyaline frills of urosomites not present. Ovary 
large, about half of body length (Fig. 1A—B). 
Genital double-somite (Figs 1A-B, 2C) wider than long; com- 
pletely fused, with weakly pronounced constriction bilaterally 
(possibly indicating original segmentation). Genital field (Fig. 2C) 
with small copulatory pore (arrowed in Fig. 2C) located in median 
depression; gonopores fused medially forming single genital slit 
covered on both sides by opercula derived from sixth legs; no 
distinct armature discernible; seminal receptacles fused forming 
large median sac. 
Anal somite (Fig. 2C—D) with well developed spinulose opercu- 
lum flanked by spinular rows; with pair of dorsal sensillae anterior 
to operculum. Caudal rami (Fig. 2C—D) longer than wide; each 
ramus with 7 setae; setae I-III and VI-VII bare, setae IV and V with 
minute spinules; setae I and II positioned dorsolaterally with seta I 
being much shorter than seta IJ; seta III positioned laterally; setae 1V 
and V fused basally, each with predesigned fracture planes at base; 
seta V longest (longer than whole urosomal segments combined); 
seta VI small; seta VII tri-articulate at base. Bases of setae typically 
surrounded by few tiny spinules. Inner margin of each ramus with 
dorsolateral concavity. 
Antennule (Fig. 3A) 8-segmented, slender; with well developed 
sclerite around base of segment 1; all setae bare. Segment 1 without 
seta; segment 3 longest; segment 4 with aesthetasc. Armature for- 
mula: 1-[0], 2-[7], 3-[7], 4-[2 + (1 + ae)], 5-[2], 6-[2], 7-[4], 8-[3 + 
acrothek]. Apical acrothek consisting of slender aesthetasc fused 
basally to 2 setae. All segments without surface ornamentation. 
Antenna (Fig. 3B) 4-segmented. Coxa small, without ornamenta- 
tion. Basis with spinules along proximal outer margin, and distal 
inner margin; abexopodal seta absent. Exopod minute, 1-segmented, 
with | pinnate apical seta. Endopod 2-segmented; proximal segment 
with 2 rows of spinules along abexopodal margin; distal segment 
